78656-79-8Relevant academic research and scientific papers
213. Synthesis of Triafulvene-Precursors from Trisubstituted Cyclopropanes
Weber, Andreas,Sabbioni, Gabriele,Galli, Roberto,Staempfli, Urs,Neuenschwander, Markus
, p. 2026 - 2033 (1988)
Trisubstituted cyclopropanes 5a-f are prepared by carbene addition to the appropriate olefins.While 5a (Y = OAc) and 5c (Y = Cl) rearrange in the presence of BuLi, 5d (Y = SPh) is stable enough to allow the envisaged sequence for triafulvene (Scheme 2); halogen-Li exchange, followed by methylation of 6d, gives 7d in a 93percent yield; after base-induced elimination of HBr from 7d, the key precursor 1-methylene-2-(phenylthio)cyclopropane (9, 70percent yield) is isolated.Compound 9 is transformed into the corresponding sulfoxide 10 (83percent), sulfone 11 (80percent), and sulfonium fluoroborate 12 (95percent yield) by subsequent oxidation and methylation, respectively.Some 1H NMR results of cyclopropanes 5a-f and 7d as well as of methylidene-cyclopropanes 9-11 are discussed.
Kupfer(II)-chlorid-katalysierte 'Carben-Dimerisierung' von 1-Halogeno-1-lithiocyclopropanen: Ein einfacher Zugang zu Bi(cyclopropylidenen)
Loosli, Thomas,Borer, Markus,Kulakowska, Iga,Minger, Andrea,Neuenschwander, Markus,Engel, Peter
, p. 1144 - 1165 (2007/10/02)
A series of 13 bi(cyclopropylidenes) 11 are prepared in a simple one-pot reaction by halogeno-lithio exchange between 1,1-dibromocyclopropanes 1a-n and BuLi, in most cases at -95 deg C, to give 1-bromo-1-lithiocyclopropanes 2a-n, followed by treatment with CuCl2 at low temperature and a simple workup at room temperature (Scheme 3c and Table 1).The yields of bi(cyclopropylidenes) 11 strongly depend on reaction parameters, as explicitly shown for the conversion 1f->-> 11f (Tables 2-8).Mixed couplings between two different carbenoids are possible (Scheme 4), while diastereoselectivity of the active transition-metal complex seems to be low.The structures of bi(cyclopropylidenes) 11 are confirmed by spectroscopic data as well as by X-ray analysis of an isolated crystalline diastereomer of 11k (Fig. 1).
