Synergistic effect of additives on cyclopropanation of olefins

Abstract

An efficient cyclopropanation of olefins with Zn(CH2I)2, a catalytic amount of CCl3CO2H, and 1,2-dimethoxyethane at room temperature is described. A wide variety of olefins, including acid-sensitive substrates, can be cyclopropanated in 71-99% yield.

Chemoselective and stereoselective lithium carbenoid mediated cyclopropanation of acyclic allylic alcohols

“…This behaviour is similar to that described for the Simmons-Smith reaction. 34,35 Spectroscopic and spectrometric data for compounds 4 and 5 are in agreement with those described in the literature. 57,58 On the other hand, reaction between geraniol and the lithium dichlorocarbenoid generated from CH 2 Cl 2 and n-BuLi led to the formation of chlorocyclopropanols 6 (40%), 7 (17%) and the double monochlorocyclopropanation product 8, in low yield (7%) (Table 1, entry 3).…”

“…Three membered rings can be formed either at the double bond proximal to the alcohol or at the distal one. Reagents based on Zn, 34,35 Sm, 36,37 Mg 38 and Ti 39 lead to cyclopropanation of the proximal double bond. Nevertheless, aluminium based reagents lead to cyclopropane formation at the distal double bond.…”

Iron‐Catalyzed Stereoconvergent 1,4‐Hydrosilylation of Conjugated Dienes

“…In addition, 9 could undergo an allyl substitution reaction with Selectfluor, [15] yielding 11 , a new type of allyl fluorine compound. Compound 9 could also be stereospecifically transformed to cyclopropane 12 by means of a Simmons–Smith cyclopropanation [16] …”

“…Compound 9 could also be stereospecifically transformed to cyclopropane 12 by means of a Simmons-Smith cyclopropanation. [16] To investigate the mechanism of these iron-catalyzed hydrosilylation reactions, we performed a series of control experiments (Scheme 5). We synthesized a formal Fe(0) Scheme 2.…”

Synthesis of β,β-Disubstituted Styrenes via Trimethylsilyl Trifluoromethanesulfonate-Promoted Aldehyde-Aldehyde Aldol Coupling-Elimination

“…The production of styrenes remains a subject of intense scrutiny owing to the prevalence of styrene building blocks in the electronics, automotive, and chemical synthesis industries . Outside the polymer industry, β,β-disubstituted styrenes specifically are valuable substrates in epoxidation, cyclopropanation, aziridination, dihydroxylation, and olefin-carbonyl cross metathesis reactions . The synthesis of β,β-dialkylstyrenes, including electron-rich styrenes, has been accomplished through a Grignard reaction-dehydration sequence, Wittig-type reactions, and metal-catalyzed cross coupling, but a robust, one-pot synthesis dependent only upon aldehyde reaction partners, which are readily available in wide variety, would be an attractive alternative.…”