Formation of 3,5-diphenyl-2-thiabicyclo[4.4.0]dec-Δ1,6-ene under the conditions of the pummerer reaction and its structure

The Pummerer rearrangement was investigated in the case of 3,5-diphenyl-2-thiabicyclo [4.4.0]decane S-oxide. It is shown that, of the two possible isomers, this compound forms only 3,5-diphenyl-2-thiabicyclo[4.4.0]dec-^1,6-ene under the conditions of the Pummerer reaction; a secondary transformation, viz., disproportionation of the latter to 3,5-diphenyl-2-thiabicyclo[4.4.0]decane and 2,4-diphenyl-5, 6-tetramethylenethiopyrylium acetate, is observed. 3,5-Diphenyl-2-thiabicyclo[4.-4.0] dec-^1,6-ene was subjected to an x-ray diffraction study; it was proved unambiguously that the C₁=C₆ double bond has a length of 1.335 Å and that the dihydrothiopyran and cyclohexene rings have a distorted half-chair conformation: the dihedral angles between the phenyl rings and the planar fragment of the heteroring are 76.8 and 93.2 °C.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1056–1059, August, 1980.     

Applications of molecular mechanics calculations in carbohydrate chemistry. I. Conformational and constitutional equilibria of tetraoxabicyclo[4.4.0]- and -[5.3.0] decanes,bicyclic diacetals of alditols

The energies of various conformations have been calculated by molecular mechanics for cis and trans isomers of 2,4,7,9-tetraoxabicyclo[4.4.0] decane and 3,5,8,10-tetraoxabicyclo[5.3.0]decane and their methyl derivatives. These molecules are models for reaction products from formaldehyde and the tetrols, pentitols, and hexitols. The conformational equilibria were analyzed for the cis-bicyclo [4.4.0] and cis-bicyclo[5.3.0] systems and compared with available experimental data. The thermodynamic stability of bicyclo[4.4.0] products was found to be higher than that of bicyclo[5.3.0] derivatives in the gas phase in every case studied. Discrepancies with experimental data that exist in a few cases can be ascribed to solvent effects.     

Stereochemical specificity of the palladium-catalyzed hydrogenation of cyclohexa[b]thiopyrans and their derivatives

Conformationally and configurationally homogeneous 2-R¹-4-R²-cis-1-thiadecalins with an equatorial orientation of the substituents attached to the C(₂) and C(₄) atoms were isolated as the final reduction products in the catalytic hydrogenation on palladium of 2-R¹-4-R²-4H(6H)-cyclohexa[b]thiopyrans, cis-3-R¹-5-R²-2-thiabicyclo[4.4.0]-^1,6-decenes, and 2-R¹-4-R²-cyclohexa[b]thiopyrylium tetrafluoroborates and trifluoroacetates. cis-3-R¹-5-R²-2-Thiabicyclo[4.4.0]-^1,6-decenes were obtained as intermediates in the incomplete reduction of 2-phenyl- and 2,4-diphenyl-4H-cyclohexa[b]thiopyrans and 2-(4-methoxyphenyl)-4-R²-cyclohexa[b]thiopyrylium salts; 2-R¹-4-R²-6H-cyclohexa[b]thiopyrans undergo complete reduction of the double bonds of the heteroring. The hydrogenation products were oxidized to sulfoxides and sulfones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 614–619, May, 1987.     

Molecular and crystal structure of ribitol 1-0-[bis(N-diethylamido)thiophosphate]-2,4; 3,5-bis-O-(N-diethylamidothionephosphate), C21H47N4O5P3S3

Conclusions X-ray diffraction structural analysis indicated that one of the products of the consecutive reaction of ribitol with PCl₃, diethylamine, and sulfur is ribitol 1-O-[bis(N-diethylamido)thionephosphate]-2,4;3,5-bis-O-(N-diethylaminothionephosphate). The six-membered heterocycles in this product are in chair conformations and form a condensed 2,4,7,9-tetraoxa-3,8-diophospha-trans-bicyclo[4.4.0]decane system with equatorial orientation of the substituents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1550–1557, July, 1985.     

Cis- und trans-1-Phosphabicyclo[4.4.0]decan

Cis- and trans-1-Phosphabicyclo[4.4.0]decane A mixture of cis-( 5a ) and trans-1-phosphabicyclo [4.4.0] decane 5b has been prepared by free-radical cyclization of (CH₂ = CH? CH₂? CH₂)₂CH? PH₂ 10 . The isomers could be separated in a pure state. Stereostructures have been assigned by ¹³C n.m.r. at 153—302 K. Equilibration of 5a and 5b by u.v. irradiation gave ?G°₃₅ ≈? 0 kJ ° mol^?1 · Activation parameters for ring inversion of “cis” stereoisomer 5a and its “cis” P-sulfid 17a are found to be ΔG° = 41.9 kJ · mol^?1 and 39.7 kJ · mol^?1, respectively. Treatment of 5a and 5b with H₂O₂, sulfur, selenium, HSO₃F, CH₃I, CS₂, and Ni(CO)₄, respectively, yield the corresponding derivatives. ¹H, ¹³C, ³¹P, ⁷⁷Se n.m.r. and i.r. data are reported.     

Conformational analysis of the stereoisomers of 3-methyl-2-oxo-2-thiabicyclo[4.4.0]decane

The conditions for the separation of the stereoisomeric sulfones and sulfoxides of 3-methyl-2-thiabicyclo[4.4.0]decane were found by means of capillary gas-liquid chromatography, and the relative thermodynamic stabilities of the latter were determined. The configuration of the stereoisomeric sulfoxides was established on the basis of oxidation data, the characteristics of the physicochemical properties, and the Kerr effect.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 621–624, May, 1976.     

Synthesis of 1, 2-diazabicyclo [4.4.0] decane and its derivatives

A new heterocyclic system, 1, 2-diazabicyclo [4.4.0] decane is synthesized, starting from-(piperidyl-2) propionic acid. The latter is converted to-(1-nitrosopiperidyl-2)-propionic acid, and thence, via-(1-aminopiperidyl-2) propionic acid, to 3-keto-1, 2-diazabicyclo [4.4.0] decane. Derivatives of 1, 2-diazabicyclo [4.4.0] decane with a substituent at position 2 are prepared.     

Equatorial preference in the C[bond]H activation of cycloalkanes: GaCl3-catalyzed aromatic alkylation reaction

GaCl(3) catalyzes the aromatic alkylation of naphthalene or phenanthrene using cycloalkanes. The C[bond]C formation predominantly takes place at the least hindered positions of the substrates, and equatorial isomers regarding the cycloalkane moiety are generally obtained. The reaction of bicyclo[4.4.0]decane and naphthalene occurs at the 2-position of naphthalene and at the 2- or 3-carbons of the cycloalkane, and the products possess a trans configuration at the junctures and an equatorial configuration at the naphthyl groups. Notably, cis-bicyclo[4.4.0]decane turns out to be much more reactive than the trans isomer, and a turnover number "TON" up to 20 based on GaCl(3) is attained. 1,2-Dimethylcyclohexane reacts similarly, and the cis isomer is more reactive than the trans isomer. Monoalkylcycloalkanes react at the secondary carbons provided that the alkyl group is smaller than tert-butyl. Adamantanes react at the tertiary 1-position. The alkylation reaction is considered to involve the C[bond]H activation of cycloalkanes with GaCl(3) at the tertiary center followed by the migration of carbocations and electrophilic aromatic substitution yielding thermodynamically stable products. The stereochemistry of the reaction reveals that GaCl(3) activates the equatorial tertiary C[bond]H rather than the axial tertiary C[bond]H.     

Synthesis of 1‐azabicyclic systems by double cyclization

5‐Cyano‐1‐azabicyclo[3.3.0]octane ( 1 ) was prepared in one step from 1,7‐dichloro‐4‐heptanone ( 4 ) under mild conditions. The application of this method for the preparation of 5‐cyano‐4,6‐dimethyl‐1‐azabicy‐clo[3.3.0]octane ( 11 ) gave two diastereomers in equilibrium. The NMR measurements of 11 and its reduced compound 15 showed that the major isomer is the cis‐exo form, and the minor isomer is the trans form. Molecular orbital calculations indicated that the cis‐exo form is more stable than the trans form, in agreement with the experimental results. Furthermore, 6‐cyano‐1‐azabicyclo[4.3.0]nonane ( 17 ) and 1‐azabicy‐clo[4.4.0]decane ( 19 ), both including a six‐membered ring, were prepared from appropriate haloketones by using this double cyclization method.     

Selective synthesis of chiral dioxabicyclo[4.4.0]decane and dioxabicyclo[5.3.0]decane from 3,4-bisallyloxy-but-1-yne derivatives via ruthenium-catalyzed en-yn-ene metathesis

We prepared a series of chiral 3,4-bisallyloxy-but-1-ynes having syn and anti configurations. Treatment of these substrates with Grubbs catalyst Cl2(PCy3)2Ru=CHPh (3 mol %) preferably gave chiral dioxabicyclo[4.4.0]decane (yields > 55%) in addition to dioxabicyclo[5.3.0]decane in minor proportions. On substitution of the 4-allyloxy group of these substrates with a 4-but-2-enyloxy group, the metathesis reactions produced only dioxabicyclo[5.3.0]decane in the presence of Grubbs ruthenium-imidazolidene carbene catalyst.     

Rate constants for the gas-phase reactions of OH radicals with a series of bi- and tricycloalkanes at 299 ± 2 K: Effects of ring strain

Relative rate constants for the gas-phase reactions of OH radicals with a series of bi- and tricyclic alkanes have been determined at 299 ± 2 K, using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with cyclohexane of 7.57 × 10^?12 cm³/molec·s, the rate constants obtained are (× 10¹² cm³/molec·s): bicyclo[2.2.1]heptane, 5.53 ± 0.15; bicyclo[2.2.2]octane, 14.8 ± 1.0; bicyclo[3.3.0]octane, 11.1 ± 0.6; cis-bicyclo[4.3.0]nonane, 17.3 ± 1.3; trans-bicyclo[4.3.0]nonane, 17.8 ± 1.3; cis-bicyclo[4.4.0]decane, 20.1 ± 1.4; trans-bicyclo[4.4.0]decane, 20.6 ± 1.2; tricyclo[5.2.1.0^2,6]decane, 11.4 ± 0.4; and tricyclo[3.3.1.1^3,7]decane, 23.2 ± 2.1. These data show that overall ring strain energies of ?4–5 kcal mol^?1 have no significant effect on the rate constants, but that larger ring strain results in the rate constants being decreased, relative to those expected for the strain-free molecules, by ratios which increase approximately exponentially with the overall ring strain.     

Synthesis and X‐ray study of cis and trans isomers of 6‐cyano‐2‐oxa‐10‐thia‐1‐phosphabicyclo[4.4.0]decane‐1‐oxide

Intramolecular cyclization of bis(3‐chloropropyl)‐diethoxythiophosphorylacetonitrile 7, taking place under distillation in vacuo, yields 6‐cyano‐2‐oxa‐10‐thia‐1‐phosphabicyclo[4.4.0]decane‐1‐oxide 10 as a mixture of cis and trans isomers in a 2.3:1 ratio. The isomers were separated chromatographically. For both isomers, single crystals with nonequivalent enantiomeric ratios were obtained under crystallization. The structures of both isomers of bicyclophostone 10 are confirmed by X‐ray study of single crystals. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:163–170, 2000     

Asymmetric metal complex hydrogenation of 1-methyl-3,4-dihydroisoquinoline in the presence of amidophosphite ligand

A number of metal complex precatalysts, solvents, and additives were examined in the asymmetric hydrogenation of 1-methyl-3,4-dihydroisoquinoline in the presence of a chiral amidophosphite ligand. The enantioselectivity of hydrogenation of this substrate increased upon addition of iodine. The best result in the selective hydrogenation was observed when [Ir(COD)₂]BARF was used as the precatalyst (COD is the cycloocta-1,5-diene, BARF is the tetrakis[3,5-bis(trifluoromethyl)phenyl]borate).     

Direct ionic chlorination of alkyl sulfones with sulfuryl chloride

The introduction of a Cl atom usually takes place at a position a to the α atom of alkyl sulfones. In this paper, a new ionic chlorination method of alkyl sulfones with sulfuryl chloride in which the most noteworthy observation was exclusive or highly selective β-chlorination of diethyl sulfone or sulfolane (tetrahydrothiophene-1,1-dioxide) is described. The most successful synthetic application of this method was exemplified by the chlorination of 7-thiabicyclo[2.2.1]heptane-7,7-dioxide, which affords 2-exo- and 2-endo-chloro-7-thiabicyclo[2.2.1]heptane-7,7-dioxides, which were difficult to obtain by the radical chlorination, probably because of the undesired homolytic SO₂C bond fission. 2-exo-Chloro-7-thiabicyclo[2.2.1]heptane-7,7-dioxide, thus obtained, was selectively reduced to give 2-exo-chloro-7-thiabicyclo[2.2.1]heptane. A mechanism for this chlorination is also discussed.     

Regioselectively [15NO2]-labeled N-methoxypicramide and DPPH prepared by using crown ether and solid sodium [15N]nitrite

The present paper reports the regioselective [¹⁵NO₂]-labeling of N-methoxy-2,4,6-trinitroaniline and 2,2-diphenyl-1-picrylhydrazine (reduced DPPH). Starting from N-methoxy-2,6-dinitroaniline, or N-methoxy-2,4-dinitroaniline, nitration in methylene chloride with solid sodium [¹⁵N]nitrite and 15-crown-5-ether afforded N-methoxy-2,6-dinitro-4-[¹⁵N]nitroaniline and N-methoxy-2,4-dinitro-6[¹⁵N]nitroaniline, respectively. The same compounds could be prepared in higher purity by nitrodecarboxylation (ipso-substitution) under the same conditions starting from N-methoxy-4-carboxy-2,6-dinitroaniline (4-methoxyamino-3,5-dinitrobenzoic acid) and N-methoxy-2-carboxy-4,6-dinitroaniline (2-methoxyamino-3,5-dinitrobenzoic acid). Similarly,ipso-substitution of 2,2-diphenyl-1-(4-carboxy-2,6-dinitrophenyl)-hydrazine afforded, under the same reaction conditions, 2,2-diphenyl-1-(2,6-dinitro-4-[¹⁵N]nitrophenyl)-hydrazine. By¹H-NMR and¹³C-NMR it was also observed that under these reaction conditions a¹⁴NO₂ group can be replaced by a¹⁵NO₂ group.     

Samarium(II) iodide-induced cascade reaction for tricyclic γ-lactone synthesis from acyclic keto diesters

Cascade reaction involving reductive cyclization, Dieckmann condensation, and lactonization of E- and Z-dimethyl 2-methyl-8-oxoundec-2-enedioates and Z-dimethyl 2-methyl-7-oxodec-2-enedioate with samarium(II) iodide was found to stereospecifically produce cis and trans bicyclo[4.4.0]decane (decalin) ring systems and trans bicyclo[4.3.0]nonan (perhydroindane) ring system each consisting of γ-lactone, respectively.     

Useful enantioselective bicyclization reactions using an N-protonated chiral oxazaborolidine as catalyst

[reaction: see text] Nine examples are reported of enantioselective [4 + 2] cycloaddition reactions of achiral, acyclic substrates to form chiral bicyclo[4.3.0]nonane or bicyclo[4.4.0]decane derivatives.     

An Unexpectedly Stable Chiral Hydrido-Solvent Complex of RuII: A mechanistic link in the enantioselective hydrogenation of pyrones. Preliminary communication

The ligand (6,6′-dimethoxybiphenyl-2,2′-diyl)bis[3,5-di(tert-butyl)phenylphosphine] ( 1 ) forms an unexpectedly stable hydrido-bis-solvento complex of composition [RuH(isopropanol)₂( 1 )]BF₄, ( 2 ) under the conditions used in the enantioselective hydrogenation of pyrones. The structure of 2 , determined by X-ray diffraction, represents the first well-characterized chiral five-coordinate bis-phosphine ruthenium-hydride complex stable as a solvento complex, and provides a structural link in the enantioselective pyrone hydrogenation cycle catalyzed by [Ru(OAc)₂( 1 )]. Using the arene complex [RuH(p-cymene)( 1 )]BF₄ ( 3 ), the chiral pocket of coordinated 1 is shown to be relatively rigid, via NMR spectroscopy. This is reflected in restricted rotation about one of the four P–[3,5-di(tert-butyl)phenyl] P? C_ipso bonds at room temperature.     

Pallambins A and B, unprecedented hexacyclic 19-nor-secolabdane diterpenoids from the Chinese liverwort Pallavicinia ambigua

Pallambins A (1) and B (2), two novel 19-nor-7,8-secolabdane diterpenoids with unprecedented tetracyclo[4.4.0(3,5).0(2,8)]decane skeletons, along with a pair of structurally related isomers, pallambins C (3) and D (4), were isolated from the Chinese liverwort Pallavicinia ambigua. Their structures with absolute configurations were determined by means of NMR, X-ray diffraction, and CD analyses. Their preliminary cytotoxicity to human cancer cells was also tested.     

Synthesis of selenium analogues of 1-azabicyclo[4.4.0]decane

An approach to the synthesis of selenium bicyclic structures of the 1-azabicyclo[4.4.0]decane series was developed, which included the condensation of aryl isoselenocyanates with 2-(2-bromoethyl)piperidine and subsequent intramolecular cyclization of selenoureas formed.