Solvent-mediated generation of cobalt-cluster-stabilised propargyl cations and radicals: allyl migration versus peroxide formation

The protonation of [Co(2)(CO)(6){9-[(allyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (4), with HBF(4) in CH(2)Cl(2) led to migration of the allyl group from silicon to the cobalt-stabilised cationic site to furnish [Co(2)(CO)(6){9-allyl-9-[(dimethylfluorosilyl)ethynyl]-9H-fluorene}] (17). However, under the same conditions, [Co(2)(CO)(6){9-[(benzyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (5) underwent desilylation and rearrangement of the resulting terminal alkyne-dicobalt complex to give [Co(3)(CO)(9)(9H-fluorenylmethylcarbynyl)] (24); moreover, dimerisation of the (benzyldimethylsilyl)ethynyl-9H-fluorenyl moiety led to the propargyl-allene 26. In contrast, protonation of 5 in THF yielded [{Co(2)(CO)(6){[(benzyldimethylsilyl)ethynyl-9H-fluorenyl])}(2)peroxide] (27) through a radical coupling process. Analogously, protonation of [Co(2)(CO)(6){9-[(vinyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (6) yields the corresponding peroxide 28. X-ray crystallographic data are reported for, among others, complexes 17, 24, 26, 27 and 28.     

Photochemical and Acid-Catalyzed Rearrangements of 4-Carbomethoxy-4-methyl-3-(trimethylsilyl)-2,5-cyclohexadien-1-one

The synthesis of 4-carbomethoxy-4-methyl-3-(trimethylsilyl)-2,5-cyclohexadien-1-one (1) in 60% overall yield from benzaldehyde is described. Irradiation (366 nm) of 1 in benzene solution gave products of type A photorearrangement; e.g., diastereomers of the 4-(trimethylsilyl)- and 5-(trimethylsilyl)bicyclo[3.1.0]hex-3-en-2-ones 8 and 9. Bicyclohexenones 9a and 9b could not be isolated, but underwent acid-catalyzed protiodesilylative rearrangements on attempted chromatography (silica gel) to give a 1:1 mixture of (E)- and (Z)-4-(carbomethoxymethylmethylene)cyclopent-2-en-1-ones 12 and 13. Irradiation (366 nm) of either 12 or 13 resulted in photoisomerization to a photostationary state that was also a 1:1 mixture. Irradiation of 8a or 8b gave equivalent mixtures of phenols 14 and 15 by way of the type B oxyallyl zwitterion 17. The available experimental evidence suggests that both 9a and 9b undergo regiospecific photorearrangement to phenol 16 with no trace of 3-methyl-4-carbomethoxyphenol (19), the product of ipso substitution of the Me(3)Si group at C(4). Phenol 15 was isolated in 65% yield from the photoreaction of 1 in benzene with 20 equiv of CF(3)CO(2)H. The acid-catalyzed rearrangement of 1 to 3-carbomethoxy-4-methylphenol (21) occurs in 91% yield by way of CO(2)Me group rearrangement to C(3) to give the Me(3)Si-stabilized carbocation 23.     

Control of two-electron four-center (2e-/4c) C-C bond formation observed for tetracyanoethenide dimerization, [TCNE]2(2-)

Cu(PPh3)3(TCNE) (TCNE = tetracyanoethylene) and 14 other examples form [TCNE]22- dimers possessing a long 2.89 +/- 0.05 A two-electron four-center (2e-/4c) C-C bond in the solid state. This bond arises from the overlap of the b2g pi* singly occupied molecular orbital (SOMO) on each [TCNE]*- fragment, forming a filled bonding orbital of b2u symmetry, and the stabilizing effect of the cation...anion interactions in the crystal that exceed the anionic repulsion. In contrast, Mn(C5H5)(CO)2(TCNE) exhibits a related, but different, [TCNE]*-...TCNE]*- motif in the solid state that lacks the 2e-/4c C-C bonding. To better understand the unusual nature of 2e-/4c C-C bonding, the genesis of the differences between their respective pi-[TCNE]*-...TCNE]*- interactions was sought. The lack of 2e-/4c C-C bond formation is attributed to the weaker radical character of the [TCNE]*- ligand, which has a total spin population of only 0.5 electron, half of that required for two S = 1/2 [TCNE]*- moieties to form a [TCNE]22- dimer. Hence, the antiferromagnetic MnII-[TCNE]*- intramolecular interaction (between the formally S = 1/2 Mn-bound [TCNE]*- and the paramagnetic Mn(II)) dominates over the intermolecular pi-[TCNE]*--[TCNE]*- spin coupling (between two S = 1/2 [TCNE]*- needed to form [TCNE]22-). Therefore, by selecting specific metal ions that can interact with sigma-[TCNE]*-, dimerization forming [TCNE]22- can be favored or disfavored.     

Pericyclic organometallic reactions. Cycloaddition reactions of (η-cycloheptatriene)Ru(CO)3. Crystal structure of tricarbonyl[(2,3,4,9-η)-bicyclo[4.2.1]non-2-ene-4,9-diyl-7,7,8,8-tetracarbonitrile]ruthenium

(η⁴-Cycloheptatriene)Ru(CO)₃ reacts with tetracyanoethylene (TCNE), 4-phenyltriazoline-3,5-dione (PTAD) and (carbomethoxy)maleic anhydride (CMA) to give stable 3 + 2 σ,π-allylic adducts. The 3 + 2 adduct with TCNE equilibrates via a [4,4]-sigmahaptotropic rearrangement with the less stable 6 + 2 adduct, which decomposes under the reaction conditions to the demetallated 6 + 2 adduct. It is concluded that σ,π-allylic adducts are in general more stable than their isomeric η⁴-π counterparts. The structure of the 3 + 2 TCNE adduct was determined by a single-crystal X-ray diffraction study.     

Diastereoselective total synthesis of isocarbacyclin from L-ascorbic acid

Diastereoselective total synthesis of isocarbacyclin, which features a fused bicyclic key intermediate available from l-ascorbic acid, is described. The key intermediate was prepared in multigram quantities by the Pauson-Khand reaction of l-ascorbic acid-based (R)-4,4-diallyl-2,2-dimethyl-5-(trimethylsilyl)ethynyl-1,3-dioxolane (3), discriminating diastereotopic groups and faces of the geminal allyl substituents.     

Ionic species produced by mechanical fracture of solid polymer. III. Anions from polytetrafluoroethylene

The tetracyanoethylene anion radical (\documentclass{article}\pagestyle{empty}\begin{document}${\rm TCNE}^{ \cdot ^ - } $\end{document}) was detected by ESR spectroscopy in polytetrafluoroethylene (PTFE), which had been mechanically fractured in vacuo with tetracyanoethylene (TCNE) at 77 K. The assignment of \documentclass{article}\pagestyle{empty}\begin{document}${\rm TCNE}^{ \cdot ^ - } $\end{document} was carried out by ESR spectral simulation on the basis of an anisotropic effective hyperfine tensor that included a forbidden transition term. The \documentclass{article}\pagestyle{empty}\begin{document}${\rm TCNE}^{ \cdot ^ - } $\end{document} is formed by abstraction of an electron by TCNE from the anion that is produced by heterogeneous scission of the carbon-carbon bond in the main chain of PTFE. At least 16% of the scission of the main chains of PTFE occurs by a heterogeneous process to produce the anions. Approximately 50% of the anions decay during annealing for 30 min at 220 K in the dark, and all anions decay within 15 min at 325 K.     

New substituent effects of the trimethylsilyl group: photochemistry of 3-trimethylsilyl-2,5-cyclohexadienones and preparation of 4-alkylidenecyclopentenones

The 4-acetoxymethyl-4-alkyl-3-trimethylsilyl-2,5-cyclohexadien-1-ones 9a-g were prepared from methyl 2-trimethylsilylbenzoate by the Birch reduction-alkylation reaction. Type A photorearrangements of 9a-g were regiospecific to give mixtures of two diastereomers of the corresponding 5-trimethylsilylbicyclo[3.1.0]hex-3-en-2-ones 11a-g. These bicyclohexenones are uniquely photostable; the diastereomers do not photointerconvert nor do they undergo the type B photorearrangement. Bicyclohexenones 11a-g undergo acid-catalyzed protiodesilylative rearrangement to give the 4-alkylidene-2-cyclopenten-1-ones 25a-g. It was of interest to find that the 4-(3'-butenyl)-2,5-cyclohexadienone 9e photorearranged to the 5-trimethylsilylbicyclo[3.1.0]hex-3-en-2-one 11e rather than undergoing the intramolecular 2 + 2 photocycloaddition. Furthermore, the 4-acetoxymethyl-3-methoxy-4-methyl-5-trimethylsilyl-2,5-cyclohexadienone 30a did not show type A photobehavior at 366 and 300 nm, while the 4-(3'-butenyl) analogue 30b gave the intramolecular 2 + 2 cycloadduct 31b. The effects of the trimethylsilyl and methoxy substituents on the photochemical reactivity of 2,5-cyclohexadien-1-ones are discussed from the perspective of n --> p* vs pi --> p* character of the triplet states of the dienones.     

TCNE dimer dianion coordination complexes, [Mn(TPA)(TCNE)]2[micro2-(TCNE)2] and [Mn(TPA)(micro4-C4(CN)8)0.5].ClO4, TPA=tris(2-pyridylmethyl)amine: synthesis, structure and magnetic properties

The structures and magnetic properties of two products that result from the reactions of [Mn(TPA)(CH3CN)2](ClO4)2, TPA=tris(2-pyridylmethyl)amine and potassium tetracyanoethylenide, KTCNE, are reported. [Mn(TPA)(TCNE)]2[mu2-(TCNE)2] (1) and [Mn(TPA)(micro4-C4(CN)8)0.5].ClO4 (2) are obtained by using two different ratios of the initial reactants. Each was intended to possess two or more cis-TCNE radical anions (TCNE*/-) as ligands. 1 is a dinuclear species that crystallizes in the triclinic system in the space group P, with a=10.4432(17), b=12.2726(16), and c=13.708(2) A; alpha=88.505(12), beta=75.560(14), and gamma=87.077(12) degrees; V=1698.9(4) A3; and Z=1 and features two metal centers each with three nearly orthogonal TCNE*/- ligands. However, the three TCNE*/- ligands are all dimerized via the formation of four-center, two-electron bonds: two bridge the two Mn(II) centers, and a third TCNE*/- ligand forms an intermolecular bond to another equivalent TCNE*/-. 2 crystallizes in the tetragonal system in the space group P42212, with a=17.170(3), b=17.170(3), and c=17.1837(6) A; V=5065.9(13) A3; and Z=8. It consists of a ribbon-like coordination polymer containing the previously observed but still relatively rare octacyanobutyl dianion. The [C4(CN)8]2- anion is derived from the dimerization of two TCNE radical anions via the formation of a new sigma bond, and each anion bridges four Mn(II) centers. Both 1 and 2 display magnetic behavior consistent with only weak antiferromagnetic coupling between the high-spin d5 Mn(II) in which the TCNE*/- are rendered diamagnetic through dimerization.     

Synthesis and reactivity of the Tl1 salts of

Synthons Tl1[TCNE]*- (1) and Tl12[TCNE]2- (2), for [TCNE]*- and [TCNE]2-, respectively, in metathesis reactions have been quantitatively prepared and characterized. The structure of 1 was solved and refined in a monoclinic unit cell at 27 degrees C [C2/c, a = 12.6966 (12) angstroms, b=7.7599 (7) angstroms, c=15.5041 (15) angstroms, beta = 96.610 (5) degrees , V= 1517.4 (2) angstroms3, Dcalcd = 2.911 gcm-3, Z=8, R1 = 0.0575, omegaR2=0.0701] and exhibits nuCN absorptions at 2,191 (s) and 2,162 (s) cm-1 consistent with metal-bound [TCNE]*-. The structure of 1 consists of a distorted square antiprismatic octacoordinate Tl1 bound to six monodentate [TCNE]*-s with TlN separations ranging from 2.901 to 3.171 angstroms averaging 3.020 angstroms, and one bidentate [TCNE]*- with TlN separations averaging 3.279 angstroms. The TlN bonding is attributed to electrostatic bonding. The [TCNE]*-s form dimerized zigzag chains with intra- and interdimer separations of 2.87 and 3.29 angstroms, respectively. The tight pi-[TCNE](2)2- dimer is diamagnetic and has the shortest intradimer [TCNE]*- distance reported. These synthons for [TCNE]*- and [TCNE]2- in metathesis reactions lead to the precipitation of, for example, TlIX (X = Cl, Br, OAc). Reaction of 1 with MnIII(porphyrin)X (X = Cl, OAc) forms the molecule-based magnets of [MnIII(porphyrin)][TCNE] composition, while the reaction of [CrI(C6H6)2]Br and (Me2N)2CC(NMe2)2Cl2, [TDAE]Cl2, with 1 forms [CrI(C6H6)2] [TCNE] and [TDAE][TCNE]2, respectively. The structure of [TDAE][TCNE]2.MeCN was solved and refined in an orthorhombic unit cell at 21 degrees C [I222, a = 10.2332(15), b = 13.341(6), c = 19.907(8) angstroms, V= 2717.7 angstroms3, Z = 4; Dcalcd = 1.216 gcm-3, R=0.083, Romega = 0.104] and exhibits upsilonCN absorptions at 2,193 (m), 2,174 (s), and 2,163 (s) cm-1 consistent with isolated [TCNE](2)2- , in contrast to the aforementioned TlI bound [TCNE](2)2-. The reaction of 2 with [TDAE]Cl2 forms [TDAE]2+[TCNE]2-.     

Lewis acid catalysed rearrangement of triterpenoids

From the whole plant of Opuntia vulgaris Mill (Cactaceae), four known triterpenoids friedelin, friedelan, 3-ol, taraxerone and taraxerol, have been isolated. Friedelan 3β-ol and friedelan-3-ol undergo a novel rearrangement with boron tribromide. Taraxeryl-acetate gives the expected β-amyrin acetate which undergoes further reactions to δ-amyrin acetate. Friedelan 3β-ol rearranges on treatment with boron trifluoride to give mainly olean 13 (18)-ene and olean 12-ene, together with an unexpected epimeric product. Mechanisms are suggested for these various reactions.     

Evidence for a double intramolecular trimethylsilyl rearrangement

A double trimethylsilyl rearrangement ion, m/z 287, C₆H₅S(OSi(CH₃)₃)₃, was observed in the isobutane chemical ionization mass spectrum of 3-trimethylsilyl-9-(2-trimethylsilylethylthio)-1-phenyl-3-phenylsulfonylnonane. The daughter mass spectrum of the protonated molecule produced the rearrangement ion, m/z 287, suggesting that the double trimethylsilyl rearrangement occurred intramolecularly.     

Electron-transfer salts of 1,2,3,4,5-pentamethylferrocene, Fe(II)(C5Me5)(C5H5). Structure and magnetic properties of two 1:1 and two 2:3 Fe(C5Me5)(C5H5) electron-transfer salts of tetracyanoethylene

The reaction of Fe(II)(C5Me5)(C5H5), FeCpCp, with percyano acceptors, A [A = C4(CN)6 (hexacyanobutadiene), TCNQF4 (perfluoro-7,7,8,8-tetracyano-p-quinodimethane), and DDQ (2,3-dichloro-5,6-dicyanobenzoquinone)], results in formation of 1:1 charge-transfer salts of [Fe(III)CpCp]*]*+[A]*- composition. With A = TCNQ (7,7,8,8-tetracyano-p-quinodimethane) a 1:2 electron-transfer salt with FeCpCp forms. With A = TCNE (tetracyanoethylene) a pair of 1:1 salts as well as a pair of 2:3 salts of [FeCpCp]2[TCNE]3.S (S = CH2Cl2, THF) have been isolated and characterized by single-crystal X-ray diffraction. [FeCpCp][TCNE] consists of parallel 1-D.D(*+)A(*-)D(*+)A(*-)D(*+)A(*-). chains, while [FeCpCp][TCNE].MeCN has a herringbone array of D(*+)A2(2-)D(*+) dimers separated by solvent molecules. Although each [TCNE](-) is disordered, the diamagnetic [TCNE]2(2-) dimer is structurally different from those observed earlier with an intradimer separation of 2.79 A. The [TCNE](-) in the 2:3 [FeCpCp]2[TCNE]3.S exists as an eclipsed diamagnetic [TCNE]2(2-) dimer with an intradimer ethylene C.C separation of 2.833 and 2.903 A for the CH2Cl2- and THF-containing materials, respectively. The bond distances and angles for all the cations are essentially equivalent, and the distances are essentially equivalent to those previously reported for [FeCp2](*+) and [FeCp2](*+) cations. The average Fe-C5H5-ring and Fe-C5Me5-ring centroid distances are 1.71 and 1.69 A, respectively, which are 0.05 A longer than reported for Fe(II)CpCp. The one-electron reduction potential for Fe(II)CpCp is 0.11 V (vs SCE). The 5 K EPR of [FeCpCp](*+)[BF4](-) exhibits an axially symmetric powder pattern with g(parallel) = 4.36 and g(perpendicular) = 1.24, and the EPR parameters are essentially identical to those reported for ferrocenium and decamethylferrocenium. The high-temperature magnetic susceptibility for polycrystalline samples of these complexes can be fit by the Curie-Weiss law, chi = C/(T - theta), with low theta values and mu(eff) values from 2.08 to 3.43 mu(B), suggesting that the polycrystalline samples measured had varying degrees of orientation. [FeCpCp][TCNE] exhibits the highest effective moment of 3.43 mu(B)/Fe and weak ferromagnetic coupling, as evidenced from the theta of 3.3 K; however, unexpectedly, it does not magnetically order above 2 K. The formation of the four phases comprising FeCpCp and TCNE emphasizes the diversity of materials that may form and the present inability to predict neither solid-state compositions nor structure types.     

Structure and magnetic ordering of a 2-D Mn(II)(TCNE)I(OH2) (TCNE = tetracyanoethylene) organic-based magnet (T(c) = 171 K)

Mn(II)(TCNE)I(OH(2)) was isolated from the reaction of tetracyanoethylene (TCNE) and MnI(2)(THF)(3), and has a 2-D structure possessing an unusual, asymmetric bonded μ(4)-[TCNE]˙(-). Direct antiferromagnetic coupling between the S = 5/2 Mn(II) and S = 1/2 [TCNE]˙(-) leads to magnetic ordering as a canted antiferrimagnet at a T(c) of 171 K.     

Synthesis of the new ring system,Pyrazolo[3,4-d][1,3]diazepine. A novel route for the synthesis of azolo[1,3]diazepines

A reduction of the nitrile group of 5-amino-4-cyano-1-methylpyrazole ( 3 ) has provided the very versatile compound 5-amino-1-methylpyrazole-4-carboxaldehyde ( 4 ). The amino group of 4 was protected using di-methylformamide dimethylacetal and the aldehyde group was then reacted with trimethylsilyl cyanide to afford the moisture sensitive compound 5-[[(dimethylamino)methylene]amino]-4-[cyano(trimethylsiloxy)-methyl]-1-methylpyrazole ( 10 ). The cyano group of the cyanohydrin 10 was reduced using a cobalt boride catalyst to afford an intermediate aminomethyl group which was involved in an in situ annulation. This reaction provided 1-methyl-1,4,5,6-tetrahydropyrazolo[3,4-d][1,3]diazepin-4-ol, a derivative of the new ring system, pyrazolo[3,4-d][1,3]diazepine.     

Synthesis and Reactions of a Stable Precursor to Dienes Containing Both Silicon and Sulfur Substituents

3-(Phenylthio)-4-(trimethylsilyl)-3-sulfolene (2) was readily prepared by chlorosulphenylation-dehydrochlorination of 3-(trimethylsilyl)-3-sulfolene (4b) . Treatment of 2 with n-butyllithium at ?105 °C followed by an alkylating agent gave only C5 alkylation products 6 demonstrating the stronger carbanion stabilizing ability of phenylthio group than that of trimethylsilyl group. 2-(Phenylthio)-3(trimethylsilyl)-1,3-butadiene (3a) was readily prepared by thermal extrusion of sulfur dioxide from 2 . Selective oxidation of 3a with MCPBA gave the sulfinyl (3b) and sulfonyl (3c) derivatives. The Diels-Alder reactions of 3a-c were studied, and the regiocontrolling power of the substituents follows the order PhS >PhSO ～ PhSO₂ >Me₃Si.     

Trimethylsilylverbindungen der Vb-Elemente. VII. Die Kristallstrukturen von Lithium-bis(trimethylsilyl)bismutid · DME und Tetrakis(trimethylsilyl)dibismutan sowie Bemerkungen zur Kristallstruktur des Bis(4-methoxyphenyl)ditellans

Trimethylsilyl Derivatives of Vb Elements. VII. Crystal Structures of Lithium Bis(trimethylsilyl)bismuthide · DME and of Tetrakis(trimethylsilyl)dibismuthane as well as Some Comments on the Crystal Structure of Bis(4-methoxyphenyl)ditellane Colourless lithium bis(trimethylsilyl)bismuthide · DME

1 1,2-Dimethoxyethan (DME); Tetrahydrofuran (THF)

1 and green, metallic lustrous tetrakis(trimethylsilyl)dibismuthane 2 crystallize isotopic to their antimony homologues [1, 2]. As it is shown by crystal structure determinations { 1 : ?90°C; I 4 2d; a = 1017,3(4); c = 3738,0(26) pm; Z = 8; R _w = 0,065; 2 : + 20°C; P2 ₁ /c; a = 680,9(4); b = 1704,8(13); c = 1197,9 (10) pm; β = 119,46(6)°; Z = 2; R _w = 0,084} both compounds form chains which in the case of bismuthide 1 are built up as screws of alternating bismuth and lithium atoms; bonding further to two trimethylsilyl groups or to the chelating DME ligand both atoms gain coordination number 4 {Li? Bi 292(3); Bi? Si 263.3(14) pm; Bi? Li? Bi 132(1); Li? Bi? Li 148(1); φ(Li? Bi? Li? Bi) 83°}. In the case of dibismuthane 2 the centrosymmetric molecules are strung, their Bi-Bi groups forming nearly linear zigzag chains with shortened intermolecular contact distances {Bi-Bi 303.5(3); Bi …? Bi 380.4(3); Bi? Si 268 pm; Bi? Bi …? Bi 169; Bi? Bi? Si 97.4(5) and 92.0(5)°}. Structure and properties of 2 are compared with those of similar compounds; the crystal structure of brown, green metallic lustrous bis(4-methoxyphenyl)ditellane 5 already published by Ludlow and McCarthy[3] is reinvestigated with respect to very short intermolecular Te…?Te contacts.     

New convergent synthesis of 1alpha,25-dihydroxyvitamin D3 and its analogues by Suzuki-Miyaura coupling between A-ring and C,D-ring parts

A new convergent method for the synthesis of 1alpha,25-dihydroxyvitamin D(3) and its analogues has been developed that involves efficient preparation of the A-ring part 1a, (Z)-(3S,5R)-1-bromomethylene-3,5-bis(tert-butyldimethylsilyloxy)-2-methylenecyclohexane, starting from epichlorohydrin (4) and its Suzuki-Miyaura coupling reaction with the C,D-ring part 12. Thus, (R)-4 was converted to (3S,5R)-5-(tert-butyldimethylsilyloxy)-8-(trimethylsilyl)-oct-1-en-7-yn-3-ol (3a) through a ten-step reaction sequence in 49% overall yield. Compound 3a thus obtained was treated with a Ti(O-i-Pr)(4)/2 i-PrMgCl reagent and then with NBS to afford (Z)-(1S,2S,5R)-2-bromomethyl-3-[bromo(trimethylsilyl)methylene]-5-(tert-butyldimethylsilyloxy)cyclohexanol (10a) in 51% yield, from which 1a was obtained in 87% yield by sequential treatment with TBSCl/imidazole, DBU, and Cs(2)CO(3). The resulting A-ring intermediate 1a was reacted with alkenylboronate 12 in the presence of a PdCl(2)(dppf) catalyst to furnish 1alpha,25-dihydroxyvitamin D(3) in 82% yield after protodesilylation. Similarly, all of the other three possible stereoisomers of A-ring parts 1b, 1c, and 1d were prepared, from which 1-epi-, 3-epi-, and 1,3-di-epi-1alpha,25-dihydroxyvitamin D(3) were synthesized by coupling with 12 in excellent yield, respectively. Starting from 1a and 1c, des-C,D-1alpha,25-dihydroxyvitamin D(3) analogues, retiferol 13 and its 3-epi derivative, were also prepared, respectively.     

Synthesis of rac-(1R,4aR,9aR)-2-methyl-1,3,4,9a-tetrahydro-2H-1,4a-propanobenzofuro[2,3-c]pyridin-6-ol. An unusual double rearrangement leading to the ortho- and para-f oxide-bridged phenylmorphan isomers

In an attempt to obtain the para-f isomer, rac-(1R,4aR,9aR)-2-methyl-1,3,4,9a-tetrahydro-2H-1,4a-propanobenzofuro[2,3-c]pyridin-6-ol, via mesylation of an intermediate 9[small alpha]-hydroxyphenylmorphan, we obtained, instead, a rearranged chloro compound with a 5-membered nitrogen ring, 7-chloro-3a-(2,5-dimethoxyphenyl)-1-methyl-octahydroindole. This indole underwent a second rearrangement to give us the desired para-f isomer. The structures of the intermediate indole and the final product were unequivocally established by X-ray crystallography. A resynthesis of the known rac-(1R,4aR,9aR)-2-methyl-1,3,4,9a-tetrahydro-2H-1,4a-propanobenzofuro[2,3-c]pyridin-8-ol, the ortho-f isomer, was achieved using the reaction conditions for the para-f isomer, as well as under Mitsunobu reaction conditions where, unusually, the oxide-bridge ring in the 5-phenylmorphan was closed to obtain the desired product. The synthesis of the para-f isomer adds an additional compound to those oxide-bridged phenylmorphans that were initially visualized and synthesized; the establishment of the structure and configuration of 8 of the theoretically possible 12 racemates has now been achieved. The X-ray crystallographic structure analysis of the para-f isomer provides essential data that will be needed to establish the configuration of a ligand necessary to interact with an opioid receptor.     

Synthesis, spectroscopic and thermal studies of the reactions of the donors piperazine and N,N′-dimethylpiperazine with σ- and π-acceptors

The interactions of the electron donors piperazine (PIP) and N,N′-dimethylpiperazine (DMPIP) with the σ-acceptor iodine and the π-acceptors tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) were studied spectrophotometrically in chloroform at 25 °C. The electronic and infrared spectra of the resulting charge-transfer complexes were recorded, in addition to thermal analysis. The results obtained showed that the stoichiometries of the reactions are not fixed and depend on the nature of both the donor and the acceptor. The formed CT-complexes have the formulas of , [(PIP)(TCNE)₂], [(PIP)(DDQ)₂], , [(DMPIP)(TCNE)₂] and [(DMPIP)(DDQ)₂]. A general mechanism explaining the formation of triiodide complexes was suggested.     

Transpositions thermiques de derives d'α-pinene

Novel thermal transformations of (+)-pin-2-en-9-al 1 and (+)-9-methyl-pin-2-en-9-one 3 by [3,3] sigmatropic mechanism to allyl vinyl ethers 2 and 4 are described. The ether 4 may undergo further rearrangement in an acid-catalysed step to the (-)-2.6-dimethylbicyclo[3.3.1]non-6-en-2ones (5 and 5'). Formation of the bicyclic ketones (+)-5 and 5' of opposite absolute configuration occurs by [3,3] sigmatropic rearrangement of the trimethylsilyl enol ether of 3 and hydrolysis. The proposed mechanism is confirmed by studying the deuterated ketone d₃^?3.