X-ray Crystal Structure, ab Initio Calculations, and Reactivity of 1,3,2lambda(5)-Diazaphosphetes: A New Type of 4-pi-Electron 4-Membered Heterocycle

The structure of P,P-bis(diisopropylamino)-4-phenyl-1,3,2lambda(5)-diazaphosphete, 1a, has been determined by a single-crystal X-ray diffraction study (C(19)H(33)N(4)P, monoclinic system, space group P2(1), a = 9.482(1) ?, b = 11.374(3) ?, c = 9.668(2) ?, beta = 97.16(1) degrees, Z = 2). According to quantum chemical calculations at an RHF level of optimization utilizing the 6-31g(d,p) basis set, 1a has a zwitterionic structure with the negative charge delocalized on the NCN allylic fragment and the positive charge localized at the phosphorus. Heterocycle 1a reacts with water and benzaldehyde affording N-phosphoranylbenzamidine 3 (95% yield) and the expected aza-Wittig adduct 4 (85% yield), respectively. Addition of 1 equiv of methyl trifluoromethanesulfonate and of 2 equiv of BH(3).THF to 1a affords cyclic phosphonium salt 5 (94% yield) and the bis(borane) adduct 6a (90% yield), respectively. Dimethyl acetylenedicarboxylate slowly reacts with 1a giving rise to 1,3,4lambda(5)-diazaphosphinine, 9, in 70% yield. The X-ray crystal structures of products 2,3, and 6a are reported (2: C(26)H(38)N(5)P, monoclinic system, space group C2/c, a = 16.337(8) ?, b = 19.810(2) ?, c = 8.800(2) ?, beta = 117.68(2) degrees, Z = 4. 3: C(19)H(35)N(4)OP, orthorhombic system, space group P2(1)2(1)2(1), a = 9.090(1) ?, b = 12.955(2) ?, c = 17.860(3) ?, Z = 4. 6a: C(19)H(39)B(2)N(4)P, orthorhombic system, space group P2(1)2(1)2(1), a = 10.340(1) ?, b = 13.247(1) ?, c = 16.996(1) ?, Z = 4).     

beta-acylvinyl anion and dianion equivalents: lithiation of 1-[(2EZ)-3-chloroprop-2-enyl]-1H-1,2,3-benzotriazole: preparation and elaboration of 1-(2-oxiranylvinyl)-1H-benzotriazoles

The allyllithium generated from 1-[(2EZ)-3-chloroprop-2-enyl]-1H-1,2,3-benzotriazole (5) and LDA, in the presence of HMPA, reacts with enolizable and nonenolizable carbonyls solely at the CCl terminus to give 1-(2-oxiranylvinyl)benzotriazoles 6a-g in 61-82% yields. Allyllithiums generated from 6a,c reacted exclusively at the CBt terminus to give 10a-d in 68-88% yields. Acidic hydrolysis of (oxiranylvinyl)benzotriazoles 6a-g and 10a-d provided 4-hydroxyalk-2-en-1-one derivatives 12a,b,c,e,g, 13a-d, and furan 14 in 54-86% yields.     

Reaction of functionalized anilines with dimethyl carbonate over NaY faujasite. 3. chemoselectivity toward mono-N-methylation

In the presence of NaY faujasite, dimethyl carbonate (MeOCO(2)Me, DMC) is a highly chemoselective methylating agent of functionalized anilines such as aminophenols (1), aminobenzyl alcohols (2), aminobenzoic acids (3), and aminobenzamides (4). The reaction proceeds with the exclusive formation of N-methylanilines without any concurrent O-methylation or N-/O-methoxy carbonylation side processes. Particularly, only mono-N-methyl derivatives [XC(6)H(4)NHMe, X = o-, m-, and p-OH; o- and p-CH(2)OH; o- and p-CO(2)H; o- and p-CONH(2)] are obtained with selectivity up to 99% and isolated yields of 74-99%. DMC, which usually promotes methylations only at T > 120 degrees C, is activated by the zeolite catalyst and it reacts with compounds 1, 2, and 4, at 90 degrees C. Aminobenzoic acids (3) require a higher reaction temperature (> or =130 degrees C).     

A succession of isomers of ruthenium dihydride complexes. Which one is the ketone hydrogenation catalyst?

Reaction of RuHCl(PPh(3))(2)(diamine) (1a, diamine = (R,R)-1,2-diaminocyclohexane, (R,R)-dach; 1b, diamine = ethylenediamine, en) with KO(t)Bu in benzene quickly generates solutions of the amido-amine complexes RuH(PPh(3))(2)(NHC(6)H(10)NH(2)), (2a'), and RuH(PPh(3))(2)(NHCH(2)CH(2)NH(2)), (2b'), respectively. These solutions react with dihydrogen to first produce the trans-dihydrides (OC-6-22)-Ru(H)(2)(PPh(3))(2)(diamine) (t,c-3a, t,c-3b). Cold solutions (-20 degrees C) containing trans-dihydride t,c-3a react with acetophenone under Ar to give (S)-1-phenylethanol (63% ee). Complexes t,c-3 have lifetimes of less than 10 min at 20 degrees and then isomerize to the cis-dihydride, cis-bisphosphine isomers (OC-6-32)-Ru(H)(2)(PPh(3))(2)(diamine) (Delta/Lambda-c,c-3a, c,c-3b). A solution containing mainly Delta/Lambda-c,c-3a reacts with acetophenone under Ar to give (S)-1-phenylethanol in 20% ee, whereas it is an active precatalyst for its hydrogenation under 5 atm H(2) to give 1-phenylethanol with an ee of 50-60%. Complexes c,c-3 isomerize to the cis-dihydride, trans-bisphosphine complexes (OC-6-13)-Ru(H)(2)(PPh(3))(2)(diamine) (c,t-3a, c,t-3b) with half-lives of 40 min and 1 h, respectively. A mixture of Delta/Lambda-c,c-3a and c,t-3a can also be obtained by reaction of 1a with KBH(Bu(sec))(3). A solution of complex c,t-3a in benzene under Ar reacts very slowly with acetophenone. These results indicate that the trans-dihydrides t,c-3a or t,c-3b along with the corresponding amido-amine complexes 2a' or 2b' are the active hydrogenation catalysts in benzene, while the cis-dihydrides c,c-3a or c,c-3b serve as precatalysts. The complexes RuCl(2)(PPh(3))(2)((R,R)-dach) or 1a, when activated by KO(t)Bu, are also sources of the active catalysts. A study of the kinetics of the hydrogenation of acetophenone in benzene catalyzed by 3a indicates a rate law: rate = k[c,c-3a](initial)[H(2)] with k = 7.5 M(-1) s(-1). The turnover-limiting step appears to be the reaction of 2a' with dihydrogen as it is for RuH(NHCMe(2)CMe(2)NH(2))(PPh(3))(2) (2c'). The catalysts are more active in 2-propanol, even without added base, and the kinetic behavior is complicated. The basic cis-dihydride c,t-3a reacts with [NEt(3)H]BPh(4) to produce the dihydrogen complex (OC-14)-[Ru(eta(2)-H(2))(H)(PPh(3))(2)((R,R)-dach)]BPh(4) (4) and with diphenylphosphinic acid to give the complex RuH(O(2)PPh(2))(PPh(3))(2)((R,R)-dach) (5). The structure of 5 models aspects of the transition state structure for the ketone hydrogenation step. Complex 2b' decomposes rapidly under Ar to give dihydrides 3b along with a dinuclear complex (PPh(3))(2)HRu(mu-eta(2);eta(4)-NHCHCHNH)RuH(PPh(3))(2) (6) containing a rare, bridging 1,4-diazabutadiene group. The formation of an imine by beta-hydride elimination from the amido-amine ligand of 2a' under Ar might explain some loss of enantioselectivity of the catalyst. The structures of complexes 1a, 5, and 6 have been determined by single-crystal X-ray diffraction.     

Synthesis and characterization of osmium(II) trispyrazolylborate complexes

Treatment of H2OsBr6 with excess 1,5-cyclooctadiene (cod) in boiling tert-butyl alcohol affords the polymer [OsBr2(cod)]x (1), which reacts with acetonitrile to form the mononuclear adduct OsBr2(cod)(CH3CN)2 (2). Polymer 1 reacts with potassium trispyrazolylborate (KTp) in ethanol to afford the hydride TpOs(cod)H (3) and the bromide complex TpOs(cod)Br (4). Bromide complex 4 reacts with sodium methoxide in methanol to afford TpOs(cod)OMe (5), which has been structurally characterized. Treatment of hydride 3 with methyl trifluoromethanesulfonate (MeOTf) in diethyl ether results in loss of methane and formation of the triflate complex TpOs(cod)OTf (6), which reacts with MgMe2 to give the methyl complex TpOs(cod)Me (7). The addition of bis(dimethylphosphino)methane (dmpm) to the known compound TpOs(PPh3)2Cl yields a mixture of the substitution products TpOs(eta1-dmpm)(PPh3)Cl (8) and TpOs(eta2-dmpm)Cl (9); the latter reacts with methyllithium to generate the methyl compound TpOs(dmpm)Me (10). NMR and IR data for these new compounds are reported. Crystal data for 5.MeOH at -80 degrees C are as follows: monoclinic, P2(1)/n, a = 10.728(1) A, b = 14.004(2) A, c = 13.906(2) A, beta = 102.42(6) degrees , V = 2040.3(5) A3, Z = 4, R(F) = 0.0247 for I > or = 2sigma(I), and R(wF2) = 0.0539 for all data.     

Simultaneous determination of copper and iron by second derivative spectrophotometry using mixtures of ligands

A highly sensitive and selective second derivative spectrophotometric method has been developed for the determination of copper and iron in mixtures. The method is based on the separation of the analytes by liquid-liquid extraction as picrate ion pairs. Iron-picrate, reacts in the organic phase of DCE with 5-phenyl-3-(4-phenyl-2-pyridinyl)-1,2,4-triazine (PPT). Similarly the copper-picrate reacts with 2,9-dimethyl-4,7-diphenyl-1,10-phenantroline (bathocuproine). The extracts were evaluated directly by derivative spectrophotometric measurement, using the zero-crossing approach for determination of copper and graphic method for iron. Iron and copper were thus determined in the ranges 8-120 ng ml(-1) and 8-125 ng ml(-1), respectively, in the presence of one another. The detection limits achieved (3sigma) were 2.9 ng ml(-1) of iron and 2.8 ng ml(-1) of copper. The relative standard deviations were in all instances less than 2.1%. The proposed method was applied to the determination of both analytes in river and tap water and the results were consistent with those provided by the AAS standard method.     

Synthesis, X-ray Crystal Structure Determination, and NMR Spectroscopic Investigation of Two Homoleptic Four-Coordinate Lanthanide Complexes: Trivalent ((t)Bu(2)P)(2)La[(&mgr;-P(t)Bu(2))(2)Li(thf)] and Divalent Yb[(&mgr;-P(t)Bu(2))(2)Li(thf)](2)(,)(1)

La(OSO(2)CF(3))(3) reacts with 4 equiv of LiP(t)Bu(2) in tetrahydrofuran to give dark red ((t)Bu(2)P)(2)La[(&mgr;-P(t)Bu(2))(2)Li(thf)] (1). Yb(OSO(2)CF(3))(3) reacts with LiP(t)Bu(2) in tetrahydrofuran in a 1:5 ratio to produce Yb[(&mgr;-P(t)Bu(2))(2)Li(thf)](2) (2) and 1/2 an equiv of (t)Bu(2)P-P(t)Bu(2). Both 1 and 2 crystallize in the monoclinic space group P2(1)/c. Crystal data for 1 at 214 K: a = 11.562 (1) ?, b = 15.914 (1) ?, c = 25.373 (3) ?, beta = 92.40 (1) degrees; V = 4664.5 ?(3); Z = 4; D(calcd) = 1.137 g cm(-)(3); R(F)() = 2.61%. Crystal data for 2 at 217 K: a = 21.641 (2) ?, b = 12.189 (1) ?, c = 20.485 (2) ?, beta = 109.01 (1) degrees; V = 5108.9 ?(3); Z = 4; D(calcd) = 1.185 g cm(-)(3); R(F)() = 2.80%. The molecular structures of 1 and 2 show the four-coordinate lanthanide atoms in distorted tetrahedral environments. These complexes are the first representatives of the lanthanide elements surrounded by four only-phosphorus-containing substituents. The main features of the crystal structure of 1 are the shortest La-P distances (2.857(1) and 2.861(1) ?) reported so far and a three-coordinate lithium cation. The molecular structure of 2 represents a divalent bis "ate" complex with two three-coordinate lithium cations. Complex 2 shows photoluminescent properties. VT NMR spectra ((7)Li and (31)P) are reported for 1and 2.     

Synthesis of phthalide derivatives using nickel-catalyzed cyclization of o-haloesters with aldehydes

The reaction of o-bromobenzoate (1 b) with benzaldehyde (2 a) in the presence of [NiBr(2)(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) and zinc powder in THF (24 hours, reflux temperature), afforded 3-phenyl-3H-isobenzofuran-1-one (3 a) in an 86 % yield. Similarly, o-iodobenzoate reacts with 2 a to give 3 a, but in a lower yield (50 %). A series of substituted aromatic and aliphatic aldehydes (2 b, 4-MeC(6)H(4)CHO; 2 c, 4-MeOC(6)H(4)CHO; 2 d, 3-MeOC(6)H(4)CHO; 2 e, 2-MeOC(6)H(4)CHO; 2 f, 4-CNC(6)H(4)CHO; 2 g, 4-(Me)(3)CC(6)H(4)CHO; 2 h, 4-C(6)H(5)C(6)H(4)CHO; 2 i, 4-ClC(6)H(4)CHO; 2 j, 4-CF(3)C(6)H(4)CHO; 2 k, CH(3)(CH(2))(5)CHO; 2 l, CH(3)(CH(2))(2)CHO) also underwent cyclization with o-bromobenzoate (1 b) producing the corresponding phthalide derivatives in moderate to excellent yields and with high chemoselectivity. Like 1 b, methyl 2-bromo-4,5-dimethoxybenzoate (1 c) reacts with tolualdehyde (2 b) to give the corresponding substituted phthalide 3 m in a 71 % yield. The methodology can be further applied to the synthesis of six-membered lactones. The reaction of methyl 2-(2-bromophenyl)acetate (1 d) with benzaldehyde under similar reaction conditions afforded six-membered lactone 3 o in a 68 % yield. A possible catalytic mechanism for this cyclization is also proposed.     

Quantum chemical and master equation simulations of the oxidation and isomerization of vinoxy radicals

The vinoxy radical, a common intermediate in gas-phase alkene ozonolysis, reacts with O2 to form a chemically activated alpha-oxoperoxy species. We report CBS-QB3 energetics for O2 addition to the parent (*CH2CHO, 1a), 1-methylvinoxy (*CH2COCH3, 1b), and 2-methylvinoxy (CH3*CHCHO, 1c) radicals. CBS-QB3 predictions for peroxy radical formation agree with experimental data, while the G2 method systematically overestimates peroxy radical stability. RRKM/master equation simulations based on CBS-QB3 data are used to estimate the competition between prompt isomerization and thermalization for the peroxy radicals derived from 1a, 1b, and 1c. The lowest energy isomerization pathway for radicals 4a and 4c (derived from 1a and 1c, respectively) is a 1,4-shift of the acyl hydrogen requiring 19-20 kcal/mol. The resulting hydroperoxyacyl radical decomposes quantitatively to form *OH. The lowest energy isomerization pathway for radical 4b (derived from 1b) is a 1,5-shift of a methyl hydrogen requiring 26 kcal/mol. About 25% of 4a, but only approximately 5% of 4c, isomerizes promptly at 1 atm pressure. Isomerization of 4b is negligible at all pressures studied.     

Reactions of Diferrocenylmorpholino- and -Methylsulfanyl-cyclopropenylium Salts with β-Dicarbonyl Compounds and Diethyl Malonate

2,3-Diferrocenyl-1-morpholinocyclopropenylium tetrafluoroborate reacts with ethyl acetoacetate, ethyl benzoylacetate, and diethyl malonate in the presence of triethylamine to yield 3-[acyl(ethoxycarbonyl)]-, 3-(diethoxycarbonyl)-methyl-3-morpholino-1,2-diferrocenylcyclopropenes (3a–c), and 3-[acyl(ethoxycarbonyl)]- and (diethoxycarbonyl)-methylidene-1,2-diferrocenylcyclopropenes (4a–c) in a ca. 1:1.5 ratio. 2,3-Diferrocenyl-1-methylsulfanylcyclopropenylium iodide with the same substrates affords compounds 4a,b (～10–15%), 3-[acyl(ethoxycarbonyl)]methyl-3-methylsulfanyl-1,2-diferrocenylcyclopropenes (5a,b) (～8–10%), 2-acyl-3,4-diferrocenyl-5-methylsulfanylcyclopentadienones (6a,b), ethyl 2-acyl-3,4-diferrocenyl-5-methylsulfanylpenta-2,4-dienoates (7a,b; 8a,b), and ethyl 3,4-diferrocenyl-2-methylsulfanyl-6-oxohexa(hepta)-2,4-dienoates (9a,b). The spatial structure of ethyl Z,E-3,4-diferrocenyl-2-methylsulfanyl-6-oxohepta-2,4-dienoate (9b) was established based on the data from x-ray diffraction analysis. Electrochemical properties of 3-[acyl(ethoxycarbonyl)]- and (diethoxycarbonyl)-methylidene-1,2-diferrocenylcyclopropenes (4a–c) are studied.     

Indoprofen类似物的合成和表征

以邻硝基苯甲醛为超始原料，合成2-溴甲基-3-喹啉酸乙酯中间体，其分别与 苯胺、2-氯代苯胺、3-氯代苯胺、2-甲基苯胺和3-甲基苯胺发生Williamson反应， Williamson反应产物经闭环反应，得到新化合物2，3-二氢-1-氧代-2-苯基-1H-吡 咯并[3，4-b]喹啉（4a），2，3-二氢-1-氧代-2-（2-氯代苯基）-1H-吡咯并[3， 4-b]喹啉（4b），2，3-二氢-1-氧代-2-（3-氯代苯基）-1H-吡咯并[3,4-b]喹啉（ 4c），2，3-二氢-1-氧代-2-（2-甲基苯基）-1H-吡咯并[3，4-b]喹啉（4d）和2， 3-二氢-1-氧代-2-（3-甲基苯基）-1H-吡咯并[3，4-b]喹啉（4e）。12个新化合物 由元素分析、红外光谱、核磁共振氢谱、质谱予以证实。     

Hydrolysis, hydrosulfidolysis, and aminolysis of imido(methyl)rhenium complexes

The tris(imido)methylrhenium complex CH3Re(NAd)3 (1a, Ad = 1-adamantyl) reacts with H2O to give CH3Re(NAd)2O (2a) and AdNH2. The resulting di(imido)oxo species can further react with another molecule of H2O to generate CH3Re(NAd)O2 (3a). The kinetics of these reactions have been studied by means of 1H NMR and UV-vis spectroscopies. The second-order rate constant for the reaction of 1a with H2O at 298 K in C6H6 is 3.3 L mol-1 s-1, which is much larger than the value 1 x 10(-4) L mol-1 s-1 obtained for the reaction between CH3Re(NAr)3 (1b, Ar = 2,6-diisopropylphenyl) and H2O in CH3CN at 313 K. Both 1a and 1b react with H2S to produce the rhenium(VII) sulfide, (CH3Re(NR)2)2(mu-S)2 (4a, R = Ad; 4b, R = Ar), with second-order rate constants of 17 and 1.6 x 10(-4) L mol-1 s-1 in C6H6 and CH3CN, respectively. Complex 4b has been structurally characterized. The crystal data are as follows: space group C2/c, a = 30.4831 (19) A, b = 10.9766 (7) A, c = 18.1645 (11) A, beta = 108.268(1) degrees, V = 5771.5 (6) A3, Z = 4. The reaction between CH3Re(NAr)2O (2b) and H2S also yields the dinuclear compound 4b. Unlike 1b, 1a reacts with aniline derivatives to give mixed imido rhenium complexes.     

An unexpected possible role of base in asymmetric catalytic hydrogenations of ketones. Synthesis and characterization of several key catalytic intermediates

The dihydrogen compound trans-[Ru((R)-BINAP)(H)(eta2-H2)((R,R)-dpen)]+ (2', BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl, dpen = 1,2-diphenylethylenediamine) is a proposed intermediate in asymmetric ketone hydrogenations. It quickly reacts at -80 degrees C with 1 equiv of the base KOtBu in 2-PrOH-d8/CH2Cl2-d2 under H2 to generate trans-Ru((R)-BINAP)(H)(2-PrO)((R,R)-dpen) (4). The alkoxide 4 does not react with H2 after hours under ambient conditions. Addition of 1 equiv of KOtBu to 4 produces a hydrogen bonded species 10 that reacts readily with H2 at -80 degrees C to generate the dihydride catalytic intermediate trans-[Ru((R)-BINAP)(H)2((R,R)-dpen)] (3'). Addition of 1 equiv of ((CH3)3Si)2NK to the alkoxide 4 produces the amide catalytic intermediate 5. Compound 5 reacts reversibly with H2 to generate 3'.     

The Uracil C(5) Position as a Metal Binding Site: Solution and X-ray Crystal Structure Studies of Pt(II) and Hg(II) Compounds

1,3-Dimethyluracil (1,3-DimeU) reacts with trans-[(CH(3)NH(2))(2)Pt(H(2)O)(2)](+) to give trans-[(CH(3)NH(2))(2)Pt(1,3-DimeU-C5)(H(2)O)]X (X = NO(3)(-), 1a, ClO(4)(-), 1b) and subsequently with NaCl to give trans-(CH(3)NH(2))(2)Pt(1,3-DimeU-C5)Cl (2) or with NH(3) to yield trans-[(CH(3)NH(2))(2)Pt(1,3-DimeU-C5)(NH(3))]ClO(4) (3). In a similar way, (dien)Pt(II) forms [dienPt(1,3-DimeU-C5)](+) (4). Reactions leading to formation of 1 and 4 are slow, taking days. In contrast, Hg(CH(3)COO)(2) reacts fast with 1,3-DimeU to give (1,3-DimeU-C5)Hg(CH(3)COO) (5). Both 1-methyluracil (1-MeUH) and uridine (urdH) react with (dien)Pt(II) initially at N(3) and subsequently with either (dien)Pt(II) or Hg(CH(3)COO)(2) also at C(5) to give the diplatinated species 7 and 9 or the mixed PtHg complex 8. C(5) binding of either Pt(II) or Hg(II) is evident from coupling of uracil-H(6) with either (195)Pt or (199)Hg nuclei and (3)J values of 47-74 Hz (for Pt compounds) and 185-197 Hz (for Hg compounds). J values of Pt compounds are influenced both by the ligands trans to the uracil C(5) position and by the number of metal entities bound to a uracil ring. Both 2 and 5 were X-ray structurally characterized. 2: monoclinic system, space group P2(1)/c, a = 15.736(6) ?, b = 11.481(6) ?, c = 25.655 (10) ?, beta = 145.55(3) degrees, V = 2621.9(28) ?(3), Z = 4. 5: monoclinic system, space group P2(1)/c, a = 4.905(2) ?, b = 18.451(6) ?, c = 11.801(5) ?, beta = 94.47(3) degrees, V = 1064.77(72) ?(3), Z = 4.     

Double geminal C-H activation and reversible alpha-elimination in 2-aminopyridine iridium(III) complexes: the role of hydrides and solvent in flattening the free energy surface

[H2Ir(OCMe2)2L2]BF4 (1) (L = PPh3), a preferred catalyst for tritiation of pharmaceuticals, reacts with model substrate 2-(dimethylamino)pyridine (py-NMe2; py = 2-pyridyl) to give chelate carbene [H2Ir(py-N(Me)CH=)L2]BF4 (2a) via cyclometalation, H2 loss, and reversible alpha-elimination. Agostic intermediate [H2Ir(py-N(Me)CH2-H)L2]BF4) (4a), seen by NMR, is predicted (DFT(B3PW91) computations) to give C-H oxidative addition to form the alkyl intermediate [(H)(eta2-H2)Ir(py-N(Me)CH2-)L2]BF4. Loss of H2 leads to the fully characterized alkyl [HIr(OCMe2)(py-N(Me)CH2-)L2]BF4 (3a(Me2CO)), which loses acetone to give alkylidene hydride 2a by rapid reversible alpha-elimination. 2a rapidly reacts with excess H2 in d6-acetone to generate [H2Ir(OC(CD3)2)2L2]BF4 (1-d12), 3a((CD3)2CO), and py-NMe2 in a 1:1:1 ratio, showing reversibility and accounting for the selective isotope exchange catalyzed by 1. Reaction of 1 with py-N(CH2)4 gives the fully characterized carbene 2c. A cis-L(2) carbene intermediate, cis-2c, observed by NMR, reacts with CO via retro alpha-elimination to give the alkyl 3cCO, while the trans isomer, 2c, does not react; retro alpha-elimination thus requires the Ir-H bond to be orthogonal to the carbene plane. Consistent with experiment, computational studies show a particularly flat PE surface with activation of the agostic C-H bond giving a less stable H2 complex, then formation of a kinetic carbene complex with cis-L, only seen experimentally for py-N(CH2)4. Hydrides at key positions, together with gain or loss of solvent and H2, flatten the PE (DeltaG) surfaces to allow fast catalysis.     

Condensation reactions of 3-oxo-2-arylhydrazonopropanals with active methylene reagents: formation of 2-hydroxy- and 2-amino-6-substituted-5-arylazonicotinates and pyrido[3,2-c]cinnolines via 6π-electrocyclization reactions

3-Oxo-3-phenyl-2-(p-tolylhydrazono)propanal (1a) undergoes condensation with ethyl cyanoacetate in acetic acid in the presence of ammonium acetate to yield either 2-hydroxy-6-phenyl-5-p-tolylazonicotinic acid ethyl ester (6a) or 2-amino-6-phenyl-5-ptolyl-azonicotinic acid ethyl ester (8), depending on the reaction conditions. Similarly, other 3-oxo-3-aryl-2-arylhydrazonopropanals 1a,b condense with active methylene nitriles 2c,d to yield arylazonicotinates 6b,c. In contrast, 2-[(4-nitrophenyl)-hydrazono]-3-oxo-3-phenyl-propanal (1c) reacts with ethyl cyanoacetate to yield ethyl 6-(4-nitrophenyl)-2-oxo-2,6-dihydropyrido[3,2–c]cinnoline-3-carboxylate (11), via a novel 6π-electrocyclization pathway. Finally, 3-oxo-2-(phenylhydrazono)-3-p-tolylpropanal (1d) condenses with 2a-c to yield pyridazinones 13a-c.     

Selectivities in reactions of organolithium reagents with unprotected 2-halobenzoic acids

[reaction: see text] Exposing 2-fluorobenzoic acid (1a) to 2.2 equiv of LTMP at ca. -78 degrees C leads to deprotonation at the 3-position whereas 2-chloro/bromobenzoic acids (1b,c) are lithiated adjacent to the carboxylate. The resulting dianions 3Li-1a and 6Li-1b,c are trapped as such by chlorotrimethylsilane. In the absence of internal quench, 6Li-1b,c isomerize to the more stable 3Li-1b,c. The latter eliminate lithium halide and set free benzyne-3-carboxylate (2) that reacts regioselectively with LTMP to give 3-tetramethylpiperidinobenzoic acid (3).     

Structural characterization of an enantiopure hydroxo-bridged binuclear iron(III) complex with empty one-dimensional helical channels

A H-bond capable chiral tetradentate ligand, Fe3+, and acetate ion assembles into a hydroxo-bridged binuclear complex with the formula [FeIII2(mu-OH)(mu-OAc)(S-L)2] x 4H2O (1) where H2S-L = S-2-(2-hydroxy-benzylamino)-3-(1H-imidazol-4-yl)-propionic acid. The crystal of 1 contains right-handed one-dimensional (1D) helical channels with 7.3-9.8 A diameter. A similar reaction with a ligand having opposite chirality forms the complex with left-handed helical channels (1a). Heating the crystals of 1 at 95 degrees C under reduced pressure selectively removes three waters from the channel forming an enantiopure porous crystal with empty channels (solvent accessible voids 18% v/v). Intermolecular hydrogen bonding between the imidazole N-H and phenolate oxygen in 1-2 forms a C6 symmetric helix with bridging hydroxo groups pointing inside the channels. All the H-bond capable atoms in the ligand along with one water molecule form an extended H-bonded network throughout the crystal. Exposing the empty channels of 2 to iodine vapor indicates partial filling of the channels with iodine. Crystal data for 1 x 4H2O include the following: hexagonal, P61, a = b = 13.164(3) A, c = 36.305 (11) A, alpha = beta = 90 degrees , gamma = 120 degrees , Z = 6, R1 = 0.0387, wR2 = 0.0842. Crystal data for 1a x 2H2O include the following: hexagonal, P6(5), a = b = 13.151(4) A, c = 36.558(2) A, alpha = beta = 90 degrees , gamma = 120 degrees , Z = 6, R1 = 0.0416, wR2 = 0.1190. Crystal data for 2 x H2O include the following: hexagonal, P61, a = b = 13.160(7) A, c = 36.559 (4) A, alpha = beta = 90 degrees , gamma = 120 degrees , Z = 6, R1 = 0.0574, wR2 = 0.1423.     

Über die Umsetzung von 1-Phenylpyrazol mit Äthylmagnesiumbromid. 8. Mitteilung über Grignard-Reaktionen [1]

In contrast to butyllithium, ethylmagnesium-bromide reacts with 1-phenyl-pyrazole exclusively by deprotonation, at the ortho position of the phenyl-ring. With nitriles the intermediate 2-(1-pyrazolyl)-phenylmagnesiumbromide gave good to excellent yields of 1-(2-aroyl or 2-hetaroyl-phenyl)-pyrazoles (Table 1, compounds 5a – 5i ); with ketones the corresponding methanol derivatives (Table 2, compounds 6a – 6c ) were found, whilst CO₂ yielded the corresponding 1-(2-carboxyphenyl)-pyrazole ( 3 ). Surprisingly enough, 1-(o-bromo-phenyl)-pyrazole and magnesium did not yield a single product, but a mixture of 3 compounds, which on reaction with 4-benzoylpyridine gave the three alcohols 19 , 20 and 21 .     

Synthesis of 1,2,4-triazol-5-ylidenes and their interaction with acetonitrile and chalcogens

Two new, more convenient methods for the synthesis of 1,2,4-triazol-5-ylidenes are described. Four new 1,2,4-triazol-5-ylidenes have been prepared using these methods: 1-(1-adamantyl)-3,4-diphenyl-1,2,4-triazol-5-ylidene (2a), 1-(1-adamantyl)-3-phenyl-4-(p-bromophenyl)-1,2,4-triazol-5-ylidene (2b), 1-(1-adamantyl)-3-phenyl-4-(alpha-naphthyl)-1,2,4-triazol-5-ylidene (2c), and 1-(1-adamantyl)-3,4-di(p-bromophenyl)-1,2,4-triazol-5-ylidene (2d). The X-ray crystal structures of 2d and the precursor salt 1-(1-adamantyl)-3,4-di(p-bromophenyl)-1,2,4-triazolium bromide (1e) are described. Compound 2a reacts with CH(3)CN via C-H insertion to form 1-(1-adamantyl)-3,4-diphenyl-5-cyanomethyl-5H-1,2,4-triazoline (3), and 2a and 2d react with elemental sulfur and elemental selenium, respectively, to form the corresponding thione (4) and selenone (5).