Scope and mechanism of cyclialkylation of alkenylmetal derivatives

Vahid Bagheri, Purdue University

Abstract

$\omega$-Haloalkenylmetals can undergo both $\sigma$- and $\pi$-type cyclization reactions. The $\sigma$ cyclialkylation reaction can provide 3- through 7-membered rings in high yields. It requires the cis relationship between Li and the $\omega$-haloalkyl group in the cyclization step. The presence of a trialkylsilyl group on the Li-bearing carbon atom facilitates configurational isomerization. However, it is not necessary for cyclization. The reaction proceeds with retention of regiochemistry. It is applicable to the synthesis of stereodefined exocyclic olefines. The cyclialkylation reactions of $\omega$-halo-1-silyl-1-alkenylmetals containing Al, Zn, Zr, or Si, on the other hand, proceed via $\pi$-type cyclization processes. The relative ease of ring formation with respect to ring size is: 3 and 4 $\gg$ 5 $<$ 6. Formation of cyclobutenylsilanes is nonregiospecific. The reaction can be effected by some polar solvents, such as THF. All of these facts can be accommodated by $\pi$-cyclization mechanisms and Baldwin's cyclization rules.

Degree

Ph.D.

Advisors

Negishi, Purdue University.

Subject Area

Organic chemistry

COinS