Facile synthesis of alkylidene cyclopentenes via palladium catalyzed ring opening of fulvene derived bicyclic hydrazines

A facile synthesis of substituted alkylidene cyclopentenes through a palladium catalyzed ring opening of fulvene derived bicyclic hydrazines with various organometallic reagents is described. The products are versatile synthons with multiple points for functionalization and can be used in the synthesis of a number of biologically active molecules.     

Crystal structure of phenyl-substituted cyclopentenes

The crystal structures of two stereoisomers of tetraphenyl- and pentaphenyl-substituted cyclopentenes 1 and 2 have been determined by X-ray analysis. An envelope conformation ¹E has been ascertained for the cis isomer 1a, whereas the cis, cis isomer 2a, which crystallizes in two different space groups, P1¯ and P2₁/n, displays a twisted ²T₁ conformation. The phenyl substituents are all tilted with respect to the cyclopentene ring in both structures. Compound 1a crystallizes in the space group P2₁/a with a = 18.553(3), b = 6.006(2), c = 19.355(5), = 102.67(4)°, and V = 2104.2(g) ų for Z = 4; compound 2a ^I crystallizes in P2₁/n with a = 10.064(2), b = 20.756(5), c = 12.245(3) Å, = 95.21(2)°, and V = 2547(1) ų for Z = 4; compound 2aII crystallizes in P1¯ with a = 10.117(3), b = 11.750(2), c = 12.359(2) Å, = 111.25(2), = 94.84(2), = 108.78(2)°, and V = 1262.3(6) ų for Z = 2.     

Gold-Catalyzed [3+2] Carbocycloaddition Reaction of Pinacol Alkenylboronates: Stereospecific Synthesis of Boryl-Functionalized Cyclopentene Derivatives

Gold-catalysis has enabled new synthetic opportunities in the chemistry of vinyldiazo compounds. Herein, we report the gold-catalyzed reaction of stabilized vinyldiazo compounds with pinacol alkenylboronates to provide boryl-functionalized cyclopentene derivatives through a formal [3+2] carbocycloaddition reaction, a very unusual pathway in alkenylboronate chemistry. This reaction proceeds with high regio- and stereoselectivity. The synthetic usefulness of the resulting borylated cyclopentene derivatives toward the synthesis of densely functionalized cyclopentanoids is also demonstrated.     

Simulation of the reaction path for the nucleophilic addition >O...C≡N from X-ray structural data

An X-ray structural investigation of 1-amino-5-ethyl-5-(hydroxyisopropoxymethyl)-2,3,3-tricyano-1-cyclopentene (1) and 5-acetyl-1-amino-4-butyl-2,3-dicyano-3-methoxyimidoyl-5-methyl-1-cyclopentene (2) has been carried out. Intramolecular non-bonded >O...CN interactions with the parameters: O...C 3.010(1) and 2.534(1) A, angles O...CN 99.3(2) and 117.5(2), C...C N 178.2(3) and 175.4(2)° have been found in both structures. A comparison of the structural parameters characterizing the non-bonded interactions in molecules1 and2 with the literature data has shown that the effectiveness of the interaction is determined not only by the O...-CN distance. It has been established that one of the parameters determining the non-bonded O...-CN interactions is the torsion angle R-O...CN.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1050–1054, June, 1993.