University of Illinois Urbana-Champaign

Synthetically Useful Dipole-Stabilized Carbanions From Thioesters and Thiocarbamates

Becker, Peter Donald

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Description

Title
Synthetically Useful Dipole-Stabilized Carbanions From Thioesters and Thiocarbamates
Author(s)
Becker, Peter Donald
Issue Date
1982
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
  • In an investigation of the formation of dipole-stabilized carbanions from thioesters, deprotonation of a tertiary center at the carbon adjacent to the sulfur of a thioester was found for the first time. Isopropyl, 2-octyl, and 4-tert-butylcyclohexyl 2,4,6-triisopropylthiobenzoates react with sec-butyllithium/TMEDA at -98(DEGREES)C to give synthetically useful (alpha)-lithio thioesters. These species react with electrophiles including primary alkyl halides and a variety of carbonyl compounds to give substituted thioesters. Study of the optically active 2-octyl thioester as well as the cis-4-tert-butylcyclohexyl thioester has shown that (alpha)-lithio thioesters are not configurationally stable. A general synthesis of trisubstituted thiiranes is provided by the action of sodium hydride on (beta)-hydroxy thioesters, which are obtained by reaction of the (alpha)-lithio thioesters with aldehydes.
  • Heptyl, neopentyl, diethylaminoethyl, methoxymethyl and allyl 2,4,6-triisopropylthiobenzoates form stable anions on reaction with sec-butyllithium/TMEDA which can be trapped with electrophiles. Ethoxyethyl and 2-methoxymethyl 2,4,6-triisopropylthiobenzoates undergo elimination to form vinyl thioesters which in turn are deprotonated adjacent to sulfur and react with electrophiles. The n-butoxymethyl 2,4,6-triisopropylthiobenzoate on the other hand decomposes to give lithium 2,4,6-triisopropylthiobenzoate.
  • The deprotonation of primary alkyl thiocarbamates adjacent to sulfur is also reported for the first time. Reaction of sec-butyllithium/TMEDA with S-ethyl and S-heptyl N,N-dimethylthiocarbamates gives the (alpha)-lithio species which react with electrophiles to give substituted thiocarbamates. These species are more readily hydrolyzed than the thioesters so they provide ready access to (alpha)-lithioalkylthiol synthons.
Graduation Semester
1982
Type of Resource
text
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http://hdl.handle.net/2142/70179

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