University of Illinois Urbana-Champaign

Studies of the Synthesis of Polycyclic Homocyclopropylcarbinols

Last, Larry Alan

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Description

Title
Studies of the Synthesis of Polycyclic Homocyclopropylcarbinols
Author(s)
Last, Larry Alan
Issue Date
1984
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Abstract
  • A new synthetic route to polycyclic homocyclopropylcarbinols has been realized by lithiation of bromocyclopropyl epoxides with n-butyllithium and subsequent intramolecular attack of the metallated cyclopropane ring onto the epoxide. A series of bromocyclopropyl epoxides was prepared from diene precursors in three or four steps by dibromocyclopropanation, epoxidation, and stereoselective reduction of one bromine atom. As an example, endo-7-bromobicyclo{4.1.0}hept-3-ene anti-oxide prepared from 1,4-cyclohexadiene underwent cyclization to endo-tricyclo{3.2.0.0('2,7)}-heptan-4-ol in 69% yield. Lithiation of a stereoisomeric mixture of the bromocyclopropyl epoxides from 1,5-hexadiene afforded the endo and exo isomers of both bicyclo{4.1.0}heptan-3-ol and bicyclo{3.1.0}hexane-2-methanol.
  • Novel concerted electrocyclic ring openings of two (beta)-lithio cyclopropyl oxiranes are described. Metalation of exo-7-bromobicyclo{4.1.0}hept-2-ene anti-oxide with n-butyllithium at 0(DEGREES)C afforded exo-bicyclo{3.2.0}hept-6-en-2-ol. A mechanism involving conrotatory ring opening to (Z,E)-cyclohepta-2,4-dienoxide, followed by conrotatory ring closure is proposed. Evidence for the intermediacy of this (Z,E)-diene was obtained by trapping with 1,3-diphenylisobenzofuran. When the metalation was carried out at -70(DEGREES)C, the major products were 2,5-di-n-butylcyclohept-3-en-1-ol and 4,5-di-n-butylcyclohept-2-en-1-ol. These compounds were evidently formed by addition of n-butyllithium to the trans double bond of the dienyl intermediate giving an allylic carbanion, which undergoes alkylation with n-butyl bromide at the termini of the allyl anion. Metalation of 8-bromobicyclo{5.1.0}oct-2-ene anti-oxide led to a similar mechanism involving the intermediacy of (Z,E)-cycloocta-2,4-dienoxide.
Graduation Semester
1984
Type of Resource
text
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http://hdl.handle.net/2142/70254

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