Ruthenium-catalyzed functionalization of aryl carbon-oxygen bonds in aromatic ethers with organoboron compounds

The ruthenium-catalyzed reaction of aryl ethers having a carbonyl group at the ortho position to the ether group with organoboronates (R-B(OCH2CMe2CH2O), R = aryl, alkenyl, and alkyl) resulted in site-selective C-C bond formation. Among the transition metal complexes screened, the RuH2(CO)(PPh3)3 complex showed the highest activity. Several aromatic ketones having methoxy or phenoxy groups at the ortho position can also be used in this coupling reaction. A variety of arylboronates containing electron-donating (NMe2, OMe, methyl, and vinyl) and -withdrawing (F and CF3) groups reacted with methoxy ketones to give the corresponding coupling products in high yields.     

Direct amination of 1-substituted 3,5-dinitrobenzenes by 1,1,1-trimethylhydrazinium iodide

The amination of 1-X-3,5-dinitrobenzenes via the vicarious nucleophilic substitution of hydrogen (VNS) with 1,1,1-trimethylhydrazinium iodide (TMHI) in the presence of t-BuOK or NaOMe in DMSO was studied. It was observed (when X = OMe, OCH(2)CF(3), OCH(2)CF(2)CF(2)H, OPh) that the amination occurs regioselectively (ratio of ortho/para-isomers is approximately 9:1) and with high yield. For X = SPh or SCH(2)Ph, the reaction proceeded with a low yield (less than 20%), with a ratio of ortho/para-isomers approximately 1:1. For X = PhSO(2) and 2 equiv of TMHI, a double amination occurs and 2,4-diamino-3,5-dinitro-1-phenylsulfonylbenzene predominates in the mixture of isomers. Under the same conditions, 1,3,5-trinitrobenzene undergoes a double amination to yield 2,4-diamino-1,3,5-trinitrobenzene. A proposed mechanism for this reaction is discussed.     

Halogenation of trifluoromethoxy and bis(trifluoromethoxy)benzene

Controlled chlorination of trifluoromethoxybenzene produced the mono-, di-, tri-, and tetrachloro derivatives. Two isomers were detected at each level of substitution. Exhaustive chlorination and bromination of 1,3- and 1,4-bis(trifluoromethoxy)-benzene yielded isomeric mixtures of only the disubstituted bis(trifluoromethoxy)benzenes. No hydrolysis of the -OCF₃ group was detected in any halogenations. The configuration of all the products was determined by ¹H and ¹⁹F nmr. A through-space hydrogen-fluorine coupling of 0.7 – 1.3Hz between the -OCF₃ substituent and the ortho proton was observed in all the halogenated products. The polychlorinated derivatives all exhibited good thermal stability at 200°–250°.     

Syntheses and experimental studies on the relative stabilities of spiro, ansa, and bridged derivatives of cyclic tetrameric fluorophosphazene

Reactions of (CF2CH2OSiMe3)2 and CF2(CF2CH2OSiMe3)2 with N4P4F8 (1) in a 1:2.5 molar ratio resulted in the formation of monospiro compounds [(CF2CH2O)2PN](F2PN)3 (2) and [CF2(CF2)CH2O)2PN](F2PN)3 (4) as well as the intermolecular bridged compounds F7N4P4OCH2CF2CF2CH2OP4N4)F7 (3) and F7N4P4OCH2CF2CF2CF2CH2OP4N4F7 (5). An equimolar reaction of dilithiated 1,3-propanediol with 1 resulted in the 1,3-ansa-substituted compound CH2(CH2O)2[P(F)N]2(F2PN)2 (6) as the major product in good yield. However, an analogous reaction of the dilithiated 1,3-propanedithiol with 1 gave only the spirocyclic compound CH2(CH2S)2(PN)(F2PN)3 (8). The molecular structures of 2 and 6 were determined by single-crystal X-ray diffraction. In the presence of catalytic amounts of CsF in THF, the bridged compound 3 was converted to the spirocyclic compound 2 while the 1,3-ansa compound 6 under similar conditions transformed into the monospiro-substituted compound CH2(CH2O)2 (PN)(F2PN)3 (7). These transformations were monitored by time-dependent 19F and 31P NMR studies.     

Relative Lewis basicities of six AI(ORF)4- superweak anions and the structures of LiA

The relative Lewis basicities of six Al(ORF)4- ions, Al[OC(CH3)(CF3)2]4-, Al(OC(CF3)3]4-, Al(OCPh(CF3)2]4-, Al[OC[4-C6H4(tBu)](CF3)2]4-, Al(OC(Cy)(CF3)2]4-, and Al(OCPh2(CF3)]4-, have been determined by measuring their relative coordinating abilities towards Li+ in dichloromethane. The relative Li- Lewis basicities of the Al(ORF)4- ions are linearly related to the aqueous pKa values of the corresponding parent HORF fluoroalcohols. The Lewis basicity of Al[OCH(CF3)2]4- could not be measured because two of these anions can coordinate to one Li+ cation. The structures of LiAl[OCH(CF3)2]4 and [1-Et-3-Me-1,3-C3H3N2][Li[Al[OCH(CF3)2)4]2] were determined.     

The structural and stereogenic properties of pentaerythritoxy-bridged cyclotriphosphazene derivatives: spiro-spiro, spiro-ansa and ansa-ansa isomers

Reactions of pentaerythritol with hexachlorocyclotriphosphazene, N3P3Cl6, and gem-disubstituted cyclotriphosphazene derivatives, N3P3Cl4R2 [R = Ph, NHBu(t) or (OCH2CF2CF2CH2O)0.5] gave a series of pentaerythritol-bridged derivatives linked spiro-spiro, spiro-ansa and ansa-ansa. The structures and stereogenic properties of the products were characterised by X-ray crystallography and 31P NMR spectroscopy on addition of the chiral solvating agent, (S)-(+)-2,2,2-trifluoro-1-(9-anthryl)ethanol. Molecules with spiro-spiro and spiro-ansa bridged gem-disubstituted cyclophosphazenes [R = Ph, NHBu(t) or (OCH2CF2CF2CH2O)0.5] are found to be chiral and exist as racemates. Molecules with ansa-ansa bridged cyclophosphazenes [R = Cl or (OCH2CF2CF2CH2O)0.5] have been characterised for the first time and are shown to have meso configurations. Analysis of crystal structure data shows that the six-membered chair form of the spiro rings and the eight-membered boat-chair form of the ansa rings in the bridged compounds are similar to analogous spiro and ansa exocyclic ring conformations of 1,3-propanedioxy-derivatives of cyclophosphazenes.     

CF3 oxonium salts, O-(trifluoromethyl)dibenzofuranium salts: in situ synthesis, properties, and application as a real CF3+ species reagent

We report in situ synthesis of the first CF(3) oxonium salts, thermally unstable O-(trifluoromethyl)dibenzofuranium salts, which furthermore have different counteranions (BF(4)-, PF(6)-, SbF(6)-, and Sb(2)F(11)-) and ring substituents (tert-butyl, F, and OCH(3)), by photochemical decomposition of the corresponding 2-(trifluoromethoxy)biphenylyl-2'-diazonium salts at -90 to -100 degrees C. The yields markedly increased in the order of BF(4)- < PF(6)- < SbF(6)- < Sb(2)F(11)-. The CF(3) oxonium salts were fully assigned by means of (1)H and (19)F NMR spectroscopy at low temperature. The CF(3) salts decomposed to form CF(4) and dibenzofurans. The half-life times at -60 degrees C of the 2-tert-butyl salts having different counteranions were 29 min for BF(4)- salt 2d, 36 min for PF(6)- salt 2c, 270 min for SbF(6)- salt 2a, and 415 min for Sb(2)F(11)- salt 2b. Those at -60 degrees C of the Sb(2)F(11)- salts having different 2-substituents were 13 min for F salt 3b, 63 min for H (unsubstituted) salt 1b, and 415 min for tert-butyl salt 2b. Thus, the stability of the CF(3) oxonium salts increased in the order of BF(4)- < PF(6)- < SbF(6)- < Sb(2)F(11)- and F < H < tert-butyl, which is in accord with the increasing orders of the non-nucleophilicity of counteranions and the electron-donating effect of ring substituents. 2-tert-Butyl-O-(trifluoromethyl)dibenzofuranium hexafluoroantimonate (2a) was thus chosen and successfully applied as a real CF(3)+ species source to the direct O- and N-trifluoromethylations of alcohols, phenols, amines, anilines, and pyridines under very mild conditions. The thermal decomposition method with a mixture of diazonium salt 17a and aryl- or alkylsulfonic acids, pyridine, or pyridines having an electron-withdrawing group also afforded CF(3)O or CF(3)N products. The trifluoromethylation mechanism is discussed and an S(N)2 mechanism containing the transient formation of free CF(3)+ is proposed. Thus, the present study has demonstrated that the exceedingly reactive CF(3)+ species can be generated much easier than the CH(3)+ species, contrary to the common sense that CF(3)+ is extremely difficult to generate in solution.     

Fluorinated bismuth alkoxides: from monomers to polymers and oxo-clusters

A series of new bismuth fluoroalkoxide compounds have been prepared through the treatment of 1,1,1,3,3,3-hexafluoro-2-propanol with BiAr3 (where Ar=Ph, p-Tol). Reactions were conducted without the use of any additional solvent and the reaction products distilled or extracted with non-polar or polar Lewis base solvents. Structural analyses reveal that under variable reaction conditions the interaction of BiAr3 with (CF3)2CHOH can give a mixture of bismuth complexes with varying degrees of substitution, cluster formation and aggregation. Compounds [Bi(OCH(CF3)2)3(pyr)2] () (pyr=pyridine), [Bi(OCH(CF3)2)3(thf)3] () (thf=tetrahydrofuran), [Bi2(OCH(CF3)2)3(dabco)3] () (dabco=1,4-diazabicyclo[2.2.2]octane), [PhBi(OCH(CF3)2)2]n (), [Bi2O(OCH(CF3)2)4(C7H8)]2 () (C7H8=toluene), [Bi9O7(OCH(CF3)2)13] (), [Bi2O(OCH(CF3)2)4(Et2O)]2 (), [Bi2O(OCH(CF3)2)4(thf)]2 () and [Bi2O(OCH(CF3)2)4(tmeda)2] () (tmeda=N,N,N',N'-tetramethylethylenediamine) have been fully characterised including by single crystal X-ray diffraction.     

Regioselective Substitution Reactions of Sulfur(VI)-Nitrogen-Phosphorus Rings: Reactions of the Halogenated Cyclic Thionylphosphazenes [NSOX(NPCl(2))(2)] (X = Cl or F) with Oxygen-Based Nucleophiles

The reactions of the cyclic thionylphosphazenes [NSOX(NPCl(2))(2)] (1, X = Cl; 2, X = F) with three oxygen-based nucleophiles of increasing basicity, sodium phenoxide (NaOPh), sodium trifluoroethoxide (NaOCH(2)CF(3)), and sodium butoxide (NaOBu) have been studied. The reaction of 1 and 2 with 4 equiv of NaOPh at 25 degrees C yielded the regioselectively tetrasubstituted species [NSOX{NP(OPh)(2)}(2)] (5d, X = Cl; 6d, X = F). Further reaction of 5d with an additional 2 equiv of NaOPh over several days or at elevated temperatures gave the fully substituted compound [NSO(OPh){NP(OPh)(2)}(2)] (5e), whereas 6d did not react further. The reaction of 1 and 2 with 5 equiv of NaOCH(2)CF(3) yielded in both cases [NSO(OCH(2)CF(3)){NP(OCH(2)CF(3))(2)}(2)] (7e), and similarly reaction with 5 equiv of NaOBu yielded [NSO(OBu){NP(OBu)(2)}(2)] (9e). In all cases, the reactions were monitored by (31)P NMR and (where applicable) (19)F NMR and were found to involve complete substitution at phosphorus via a predominantly vicinal pathway, followed by substitution at sulfur. Substitutional control of the reactions of NaOPh, NaOBu, with 1 and 2 was found to conform to the following general order of reactivity, PCl(2) > PCl(OR) > SOX (X = Cl, F). Although the reaction with NaOCH(2)CF(3) followed the same order of reactivity, a significant enhancement of reaction rate was detected with each equivalent of trifluoroethoxide added. Reaction of 7e with excess NaOCH(2)CF(3) led to elimination of (CF(3)CH(2))(2)O and the formation of the salts Na[NSO(OCH(2)CF(3))NP(OCH(2)CF(3))(2)NP(OCH(2)CF(3))O] (11) and Na[NS(O)O{NP(OCH(2)CF(3))(2)}(2)] (12). Crystals of 6d are triclinic, space group P&onemacr;, with a = 9.789(3) ?, b = 11.393(4) ?, c = 12.079(5) ?, alpha = 107.40(3) degrees, beta = 91.23(3) degrees, gamma = 93.18(3), V = 1283.6(8) ?(3), and Z = 2. Crystals of 5e are monoclinic, space group C2/c, with a = 32.457(3) ?, b = 10.747(1) ?, c = 18.294(2) ?, beta = 110.37(1) degrees, V = 5982.4(9) ?(3), and Z = 8.     

Syntheses of ketonated disulfide-bridged diruthenium complexes via C-H bond activation and C-S bond formation

The alpha-C-H bonds of 3-methyl-2-butanone, 3-pentanone, and 2-methyl-3-pentanone were activated on the sulfur center of the disulfide-bridged ruthenium dinuclear complex [(RuCl(P(OCH3)3)2)2(mu-S2)(mu-Cl)2] (1) in the presence of AgX (X = PF6, SbF6) with concomitant formation of C-S bonds to give the corresponding ketonated complexes [(Ru(CH3CN)2(P(OCH3)3)2)(mu-SSCHR1COR2)(Ru(CH3CN)3(P(OCH3)3)2)]X3 ([5](PF6)3, R1 = H, R2 = CH(CH3)2, X = PF6; [6](PF6)3, R1 = CH3, R2 = CH2CH3, X = PF6; [7](SbF6)3, R1 = CH3, R2 = CH(CH3)2, X = SbF6). For unsymmetric ketones, the primary or the secondary carbon of the alpha-C-H bond, rather than the tertiary carbon, is preferentially bound to one of the two bridging sulfur atoms. The alpha-C-H bond of the cyclic ketone cyclohexanone was cleaved to give the complex [(Ru(CH3CN)2(P(OCH3)3)2)(mu-SS-1- cyclohexanon-2-yl)(Ru(CH3CN)3(P(OCH3)3)2)](SbF6)3 ([8](SbF6)3). And the reactions of acetophenone and p-methoxyacetophenone, respectively, with the chloride-free complex [(Ru(CH3CN)3(P(OCH3)3)2)2(mu-S2)]4+ (3) gave [(Ru(CH3CN)2(P(OCH3)3)2)(mu-SSCH2COAr)(Ru(CH3CN)3(P(OCH3)3)2)](CF3SO3)3 ([9](CF3SO3)3, Ar = Ph; [10](CF3SO3)3, Ar = p-CH3OC6H4). The relative reactivities of a primary and a secondary C-H bond were clearly observed in the reaction of butanone with complex 3, which gave a mixture of two complexes, i.e., [(Ru(CH3CN)2(P(OCH3)3)20(mu-SSCH2COCH2CH3)(Ru(CH3CN)3(P(OCH3)3)2)](CF3SO3)3 ([11](CF3SO3)3) and [(Ru(CH3CN)2(P(OCH3)3)2)(mu-SSCHCH3COCH3)(Ru(CH3CN)3(P(OCH3)2)](CF3SO3)3 ([12](CF3SO3)3), in a molar ratio of 1:1.8. Complex 12 was converted to 11 at room temperature if the reaction time was prolonged. The relative reactivities of the alpha-C-H bonds of the ketones were deduced to be in the order 2 degrees > 1 degree > 3 degrees, on the basis of the consideration of contributions from both electronic and steric effects. Additionally, the C-S bonds in the ketonated complexes were found to be cleaved easily by protonation at room temperature. The mechanism for the formation of the ketonated disulfide-bridged ruthenium dinuclear complexes is as follows: initial coordination of the oxygen atom of the carbonyl group to the ruthenium center, followed by addition of an alpha-C-H bond to the disulfide bridging ligand, having S=S double-bond character, to form a C-S-S-H moiety, and finally completion of the reaction by deprotonation of the S-H bond.     

Kinetics and mechanisms of CF3CHFOCH3, CF3CHFOC(O)H, and FC(O)OCH3 reactions with OH radicals

The kinetics and mechanism of oxidation of CF3CHFOCH3 was studied using an 11.5-dm3 environmental reaction chamber. OH radicals were produced by UV photolysis of an O3-H2O-He mixture at an initial pressure of 200 Torr in the chamber. The rate constant of the reaction of CF3CHFOCH3 with OH radicals (k1) was determined to be (1.77 +/- 0.69) x 10(-12) exp[(-720 +/- 110)/T] cm3 molecule(-1)(s-1) by means of a relative rate method at 253-328 K. The mechanism of the reaction was investigated by FT-IR spectroscopy at 298 K. CF3CHFOC(O)H, FC(O)OCH3, and COF2 were determined to be the major products. The branching ratio (k1a/k1b) for the reactions CF3CHFOCH3 + OH --> CF3CHFOCH2* + H2O (k1a) and CF3CHFOCH3 + OH --> CF3CF*OCH3 + H2O (k1b) was estimated to be 4.2:1 at 298 K from the yields of CF3CHFOC(O)H, FC(O)OCH3, and COF2. The rate constants of the reactions of CF3CHFOC(O)H (k2) and FC(O)OCH3 (k3) with OH radicals were determined to be (9.14 +/- 2.78) x 10(-13) exp[(-1190 +/- 90)/T] and (2.10 +/- 0.65) x 10(-13) exp[(-630 +/- 90)/T] cm3 molecule(-1)(s-1), respectively, by means of a relative rate method at 253-328 K. The rate constants at 298 K were as follows: k1 = (1.56 +/- 0.06) x 10-13, k2 = (1.67 +/- 0.05) x 10-14, and k3 = (2.53 +/- 0.07) x 10-14 cm3 molecule(-1)(s-1). The tropospheric lifetimes of CF3CHFOCH3, CF3CHFOC(O)H, and FC(O)OCH3 with respect to reaction with OH radicals were estimated to be 0.29, 3.2, and 1.8 years, respectively.     

Photochemical cleavage and release of para-substituted phenols from alpha-keto amides

In aqueous media alpha-keto amides 4-YC6H4OCH2COCON(R)CH(R')CH3 (5a, R = Et, R' = H; 5b, R = iPr, R' = Me) with para-substituted phenolic substituents (Y = CN, CF3, H) undergo photocleavage and release of 4-YC6H4OH with formation of 5-methyleneoxazolidin-4-ones 7a,b. For both 5a,b quantum yields range from 0.2 to 0.3. The proposed mechanism involves transfer of hydrogen from an N-alkyl group to the keto oxygen to produce zwitterionic intermediates 8a-c that eliminate the para-substituted phenolate leaving groups. The resultant imminium ions H2C=C(OH)CON+(R)=C(R')CH3 9a,b cyclize intramolecularly to give 7a,b. The quantum yields for photoelimination decrease in CH3CN, CH2Cl2, or C6H6 due to competing cyclization of 8a,b to give oxazolidin-4-one products which retain the leaving group 4-YC6H4O- (Y = H, CN). A greater tendency to undergo cyclization in nonaqueous media is observed for the N,N-diethyl amides 5a than the N,N-diisopropyl amides 5b. With para electron releasing groups Y = CH3 and OCH3 quantum yields for photoelimination significantly decrease and 1,3-photorearrangment of the phenolic group is observed. The 1,3-rearrangement involves excited state ArO-C bond homolysis to give para-substituted phenoxyl radicals, which can be observed directly in laser flash photolysis experiments.     

Theoretical study of the reactions CF3CH2OCHF2 + OH/Cl and its product radicals and parent ether(CH3CH2OCH3) with OH

A dual-level direct dynamic method is employed to study the reaction mechanisms of CF3CH2OCHF2 (HFE-245fa2; HFE-245mf) with the OH radicals and Cl atoms. Two hydrogen abstraction channels and two displacement processes are found for each reaction. For further study, the reaction mechanisms of its products (CF3CH2OCF2 and CF3CHOCHF2) and parent ether CH3CH2OCH3 with OH radical are investigated theoretically. The geometries and frequencies of all the stationary points and the minimum energy paths (MEPs) are calculated at the B3LYP/6-311G(d,p) level. The energetic information along the MEPs is further refined at the G3(MP2) level of theory. For reactions CF3CH2OCHF2 + OH/Cl, the calculation indicates that the hydrogen abstraction from --CH2-- group is the dominant reaction channel, and the displacement processes may be negligible because of the high barriers. The standard enthalpies of formation for the reactant CF3CH2OCHF2, and two products CF3CH2OCHF2 and CF3CHOCHF2 are evaluated via group-balanced isodesmic reactions. The rate constants of reactions CF3CH2OCHF2 + OH/Cl and CH3CH2OCH3 + OH are estimated by using the variational transition state theory over a wide range of temperature (200-2000 K). The agreement between the theoretical and experimental rate constants is good in the measured temperature range. From the comparison between the rate constants of the reactions CF3CH2OCHF2 and CH3CH2OCH3 with OH, it is shown that the fluorine substitution decreases the reactivity of the C--H bond.     

Structure and barrier to methyl group internal rotation for (CF3)2CFCF2OCH3 and its isomer n-C4F9OCH3 (HFE-7100)

The hydrofluoroether C(4)F(9)OCH(3) (methoxynonafluorobutane, HFE-7100) has been studied by chirped pulse Fourier transform microwave spectroscopy as vapor from the liquid participates in a supersonic expansion of argon. Two isomers are present, (CF(3))(2)CFCF(2)OCH(3) and n-C(4)F(9)OCH(3), and in each case the rotational spectra of only one, dominating, conformer has been assigned. Rotational constants, centrifugal distortion constants, and barriers to methyl group internal rotation for the observed species have been experimentally determined for the first time. We note that Ray's asymmetry parameter for the (CF(3))(2)CFCF(2)OCH(3) isomer is 0.007?083(1), indicating almost "perfect" asymmetry. Also, electronic structure calculations show an extremely short C(frame)-O ether bond length of 1.337 ?.     

Rate constants for the reactions of hydroxyl radical with several fluoroethers by the relative rate method

Relative rate experiments were used to measure ratios of chemical kinetics rate constants as a function of temperature for the reactions of OH with eight fluoroethers, including CF3OCF2CHF2, CF3OCF2CHFCF3, CHF2CF2OCHF2, CF3CHFCF2OCH2CF3, (CF3)2CHOCHF2, CF2HCF2OCH2CF3, CHF2CF2OCHFCF3, and CF3CH2OCH2CF3. The temperature ranges were about 270-400 K. Each compound was measured against at least two references. Results are compared with previous data where available. An approach using model compounds for the approximate estimation of rate constants for the fluoroethers is discussed. Observed temperature dependences for fluoroethers from the present work and some literature work are shown to be accurately predictable, based on a previously determined correlation of k298K with the pre-exponential factor, A, in the Arrhenius equation k = Ae(-E/RT).     

Polyurethanes containing oxetane-derived poly(2,2-substituted-1,3-propylene oxide) soft blocks: copolymer effect on wetting behavior

Hydroxy-terminated poly(2,2-substituted-1,3-propylene oxide) telechelics and co-telechelics bearing semifluorinated (R = -CH(2)OCH(2)(CF(2))(n)CF(3), n = 0, 1) and/or bromomethyl pendant groups were synthesized from the corresponding 3,3-substituted oxetanes. The new telechelics were incorporated in polyurethanes (PUs) with isophorone diisocyanate (IPDI) and 1,4-butanediol (BD) as the hard block. Surface properties were evaluated using tapping mode atomic force microscopy (TM-AFM) and dynamic contact angle (DCA) analysis. Interestingly, polyurethanes containing P(3FOx-BrOx) have higher theta(adv) and lower theta(rec) than the homo-telechelic PUs [P(3FOx) = poly(2-methyl-2-trifluoroethoxymethyl-1,3-propylene oxide; P(BrOx) = poly(2-methyl-2-bromomethyl-1,3-propylene oxide)]. For IPDI-BD(40)/P(3FOx/BrOx-1:1), theta(adv) (116 degrees) is higher and theta(rec) (32 degrees) is lower (Deltatheta, 84 degrees ) than any other homo- or co-telechelic polyurethane. The unusual wetting behavior for P(FOx/BrOx) polyurethanes is correlated with FOx-BrOx dyad content, and a reversible H-bonding mechanism is proposed to explain the results.     

Enolate ions as beta-activators of ortho-metalation: direct synthesis of 3-aminoindenones

beta-Ketonitriles derived from a Claisen condensation of benzoate esters with alkyl- or phenylacetonitriles lead to 3-aminoindenones in the presence of excess LDA. This new reaction is also applicable to pyridine carboxylic esters. All of the 3-aminoindenones and their aza analogues can be hydrolyzed by acid to give the corresponding 1,3-indandiones. The mechanism of the reaction falls into the directed-ortho-metalation class in which the initial enolate ion of the keto-nitrile directs self-metalation at an ortho position. The new anion then cyclizes onto the nitrile group to generate an aminoindenone. Surprisingly the simplest member of the series, benzoylacetonitrile, does not undergo cyclization. Mechanistic isotope studies revealed that this substance preferentially and directly forms a dianion on the side chain, which is not further deprotonated at the ortho position of the aromatic ring.     

Lability of the trifluoromethyl group of trifluoromethoxybenzenes under HF/Lewis acid conditions

The trifluoromethyl functionality of trifluoromethoxybenzenes (trifluoromethyl phenyl ethers) becomes labile under HF/Lewis acid conditions. Substrates with an unsubstituted para-position shed their -CF₃ groups while performing a Friedel-Crafts reaction upon another substrate molecule's trifluoromethoxy group to generate p-rosolic acids. Substrates that had blocking groups at the para-positions reacted ortho. The electron donating substituents methoxy and phenoxy interfered with the formation of rosolic acids.     

Analysis of the intermolecular interactions between CH3OCH3, CF3OCH3, CF3OCF3, and CH2F2, CHF3

The intermolecular interaction energy curves of CH(3)OCH(3)-CH(2)F(2), CF(3)OCH(3)-CH(2)F(2), CF(3)OCF(3)-CH(2)F(2), CH(3)OCH(3)-CHF(3), CF(3)OCH(3)-CHF(3), and CF(3)OCF(3)-CHF(3) complexes were calculated by the MP2 level ab initio molecular orbital method using the 6-311G** basis set augmented with diffuse polarization functions. We investigate the fluorine substitution effects of both methane and dimethyl ether on intermolecular interactions. In addition, orientation dependence of intermolecular interaction energies is also studied with utilizing eight types of orientations. Our analyses demonstrate that partial fluorinations of methane make electrostatic interaction dominant, and consequently enhance attractive interaction at several specific orientations. On the contrary, fluorine substitutions of dimethyl ether substantially decrease the electrostatic interaction between ether and CH(2)F(2) or CHF(3); thus, there is no such characteristic interaction between the C-H of fluorinated methane and ether oxygen of CF(3)OCF(3) as conventional hydrogen bonding, due to reduced polarity of fluorinated ether. The combination of different pairs of the electrostatic interaction is therefore responsible for the intermolecular interaction differences among the complexes investigated herein and also their orientations.     

Reactions of halogenated hydroperoxides and peroxyl and alkoxyl radicals from isoflurane in aqueous solution

Model systems, based on aqueous solutions containing isoflurane (CHF(2)OCHClCF(3)) as an example, have been studied in the presence and absence of methionine (MetS) to evaluate reactive fates of halogenated hydroperoxides and peroxyl and alkoxyl radicals. Primary peroxyl radicals, CHF(2)OCH(OO*)CF(3), generated upon 1-e-reduction of isoflurane react quantitatively with MetS via an overall two-electron oxidation mechanism to the corresponding sulfoxide (MetSO). This reaction is accompanied by the formation of oxyl radicals CHF(2)OCH(O*)CF(3) that quantitatively rearrange by a 1,2-hydrogen shift to CHF(2)OC*(OH)CF(3). According to quantum-chemical calculations, this reaction is exothermic (DeltaH = -5.1 kcal/mol) in contrast to other potentially possible pathways. These rearranged CHF(2)OC*(OH)CF(3) radicals react further via either of two pathways: (i) direct addition of oxygen or (ii) deprotonation followed by fluoride elimination resulting in CHF(2)OC(O)CF(2)*. Route i yields the corresponding CHF(2)OC(OO*)(OH)CF(3) peroxyl radicals, which eliminate H+/O(2)*-. The resulting ester, CHF(2)OC(O)CF(3), hydrolyzes further, accounting for the formation of HF, trifluoroacetic acid, and formic acid with a contribution of 45% and 80% in air- and oxygen-saturated solutions, respectively. A competitive pathway (ii) involves the reactions of the secondary peroxyl radicals, CHF(2)OC(O)CF(2)OO*. The two more stable of the three above mentioned peroxyl radicals can be distinguished through their reaction with MetS. Although the primary CHF(2)OCH(OO*)CF(3) oxidizes MetS to MetSO in a 2-e step, the majority of the secondarily formed CHF(2)OC(O)CF(2)OO* reacts with MetS via a 1-e transfer mechanism, yielding CHF(2)OC(O)CF(2)OO-, which eventually suffers a total breakup into CHF(2)O- + CO(2) + CF(2)O. Quantum-chemical calculations show that this reaction is highly exothermic (DeltaH = -81 kcal/mol). In air-saturated solution this pathway accounts for about 35% of the overall isoflurane degradation. Minor products (10% each), namely, oxalic acid and carbon monoxide originate from oxyl radicals, CHF(2)OC(O)CF(2)O* and CHF(2)OCH(O*)CF(3). An isoflurane-derived hydroperoxide CHF(2)OCH(OOH)CF(3) in high yield was generated in radiolysis of air-saturated solutions containing isoflurane and formate either via a H-atom abstraction from formate by the isoflurane-derived peroxyl radicals or by their cross-termination reaction with superoxide O(2)*-. CHF(2)OCH(OOH)CF(3), is an unstable intermediate whose multistep hydrolysis is giving H(2)O(2) + 2HF + HC(O)OH + CF(3)CH(OH)(2). In the absence of MetS, about 55% of CHF(2)OCH(OO*)CF(3) undergo termination via the Russell mechanism and 27% are involved in cross-termination with superoxide (O(2)*-) and peroxyl radicals derived from t-BuOH (used to scavenge *OH radicals). The remaining 18% of the primary peroxyl radicals undergo termination via formation of alkoxyl radicals, CHF(2)OCH(O*)CF(3).