CYCLIALKYLATION OF ALKENYLMETAL DERIVATIVES: SCOPE AND MECHANISM
Abstract
The hydro- and carbometallation of (omega)-halo-1-metallo-1-alkynes produces (omega)-halo-1,1-dimetallo-1-alkenes which may participate in a highly regioselective (pi)-type cyclization process that is independent of the stereochemistry of the organometallic intermediate. The reaction requires two metal functions of intermediate electronegativity, including those of Al, B, Si, Zn, and Zr, and is applicable to the synthesis of 3-, 4-, and 6-membered rings. (Z)-(omega)-bromo-1-lithio-1-alkenes, generated from the corresponding alkenyl iodides via Li-halogen exchange, and which may incorporate but do not require a second metal function, undergo a regiospecific (sigma)-type cyclization that is applied to the preparation of 4- through 7-membered rings. (beta),(beta)-Disubstituted alkenylalanes, prepared by the Zr-promoted carboalumination of 1-alkynes, are stereospecifically converted into alkenyl derivatives of B, P, S, Se, and Zr by reactions with the appropriate electrophiles.
Degree
Ph.D.
Subject Area
Organic chemistry
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