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Cyclizations during the Grignard Reactions of co-Bromoalkynes

Jack K. Crandall ; Department of Chemistry, Indiana University, Bloomington, IN 47405
William J. Michaely ; Department of Chemistry, Indiana University, Bloomington, IN 47405
François Collonges ; Department of Chemistry, Indiana University, Bloomington, IN 47405
Deanna J. Nelson ; Department of Chemistry, Indiana University, Bloomington, IN 47405
Timothy A. Ayers ; Department of Chemistry, Indiana University, Bloomington, IN 47405
Joseph J. Gajewski ; Department of Chemistry, Indiana University, Bloomington, IN 47405

Sažetak

The Grignard reactions of a number of (ö-bromoalkynes have been shown to undergo regioselective cyclizations in certain instances to give the smaller possible carbocycle. These cyclizations are shown to result from two competing processes, whose relative efficiencies depend upon the chain length and the remote substitutent on the acetylene. These are interpreted as a radical cyclization which occurs only during the time the Grignard is being formed from the bromide and an organometallic reaction which slowly transforms the Grignard reagent into its cyclic isomer. The mechanistic details of these transformations are discussed.

Ključne riječi

Hrčak ID:

135984

URI

https://hrcak.srce.hr/135984

Datum izdavanja:

2.12.1996.

Posjeta: 1.102 *