Enantioselective Cyclopropanation of Allylic Alcohols with Dioxaborolane Ligands:  Scope and Synthetic Applications

Abstract

A very effective chiral controller has been found for the conversion of allylic alcohols into the corresponding enantiomerically enriched cyclopropanes using bis(iodomethyl)zinc. A variety of chiral, nonracemic cyclopropylmethanols could be obtained according to this method. This methodology was extended with success to the cyclopropanation of unconjugated and conjugated polyenes and homoallylic alcohols. The cyclopropanation of allylic carbamates has also been investigated with this system, but it was found that enantioenriched cyclopropylmethylamines are best prepared from enantioenriched cyclopropylmethanols.

Stereoselective Lewis Acid Mediated [1,3] Ring Contraction of 2,5‐Dihydrooxepins as a Route to Polysubstituted Cyclopentenes

“…With this approach in mind, we sought to apply the protocol of Charette et al [15] as a means of introducing further substitutents onto the cyclopropane and affording a tetrasubstituted cyclopentene on [1,3] rearrangement. 2,5-Dihydrooxepin 25 was synthesized in an enantioenriched form using the Charette-Simmons-Smith protocol.…”

“…2,5-Dihydrooxepin 25 was synthesized in an enantioenriched form using the Charette-Simmons-Smith protocol. [15] When 25 was subjected to the optimized reaction conditions, 26 was isolated in 70 % yield and 95 % ee [Eq. (3)].…”

The Chemistry and Biology of Epothilones—The Wheel Keeps Turning

“…[112] Highly efficient synthetic routes to these analogues were subsequently developed by Nicolaou and co-workers, which also provided access to structures incorporating additional modifications (apart from the epoxide!cyclopropane exchange; see below). [113,114] As an example, Scheme 2 summarizes Nicolaou's synthesis of cyclopropyl-Epo B analogue 9, which relies on the early installment of the cyclopropane moiety through Charette cyclopropanation [115] of cis-geraniol 10. The resulting cyclopropane 11 was elaborated into iodide 12, which served as an electrophile in the alkylation of the (À)-SAMP hydrazone 13 under Enders conditions.…”

Present and Future of Cyclopropanations in Fragrance Chemistry

“…The synthesis of (þ)-bicyclohumulenone (19) was another milestone [9], because it represents a beautiful application of the asymmetric variant of the Furukawa reaction as developed by Charette et al [10]. After an eight-step desymmetrization of 3,3-dimethylglutaric acid (15), only the unprotected allylic alcohol function of 16 is cyclopropanated with in situ formed Zn(CH 2 I 2 ), after complexation with bifunctional ligand 17.…”

“…As in the synthesis of Javanol (6a) under SimmonsÀSmith conditions, the proximal C¼C bonds of geraniol (9a) or nerol (9b; Fig. 3) are preferentially cyclopropanated, and, in the presence of the chiral ligand 17 [10], with excellent enantioselectivities [16].…”