Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, and trimethylgermyl derivatives of 3,3-dimethylcyclopropene VI: Application of observed trends to stannyl derivatives

The effects of substitution of X = C by Si or Ge in X(CH3) 3 moieties attached to the formal double bond of 3,3- dimethylcyclopropene are examined. Regularities in observed trends of vibrational frequencies implicating the moieties containing the X atom, as the X atomic mass is increased, are extrapolated to X = Sn. The results of this extrapolation made it possible to assign the known experimental vibrational frequencies of 3,3-dimethyl-1-(trimethylstannyl)cyclopropene and 3,3-dimethyl-1,2-bis(trimethylstannyl)cyclopropene. © 2004 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, and trimethylgermyl derivatives of 3,3-dimethylcyclopropene III. 3,3-dimethyl-1-(trimethylsilyl)cyclopropene

The experimental Raman and IR vibrational spectra of 3,3-dimethyl-1-(trimethylsilyl)cyclopropene in the liquid phase were recorded. Total geometry optimisation was carried out at the HF/6-31G* level and the HF/6-31G*//HF/6-31G* force field was computed. This force field was corrected by scale factors determined previously (using Pulay's method) for correction of the HF/6-31G*//HF/6-31G* force fields of 3,3-dimethylbutene-1, 1-methyl-, 1,2-dimethyl-, and 3,3-dimethylcyclopropene. The theoretical vibrational frequencies calculated from the scaled quantum mechanical force field and the theoretical intensities obtained from the quantum mechanical calculation were used to construct predicted spectra and to perform the vibrational analysis of the experimental spectra. © 2003 Elsevier Science B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Stereoconvergent Generation of a Contrasteric syn-Bicyclopropylidene (=syn-Cyclopropylidenecyclopropane) by Stille-Like Coupling

Stereoisomerically pure endo- and exo-7-halo-7-(trimethylstannyl)benzonorcar-3-enes (¼endo- and exo-(1-halo-1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalen-1-yl)trimethylstannane) 4 and 6 were selectively obtained by lithium-tin or magnesium-tin transmetalation in good yields (Scheme 2 and 3). The reaction of these compounds with copper(I) thiophene-2-carboxylate (CuTC) produced in both cases the corresponding CS-symmetric bicyclopropylidene (¼cyclopropylidenecyclopropane) syn-1, a single diastereoisomer (Schemes 5 and 6). The structure of syn-1 was undoubtedly elucidated by X-ray single crystal diffraction. The coupling mechanism of the carbenoid cyclopropane is discussed (Scheme 7)