1,6-Addition of organocopper reagents to 3-alkynyl-2-cycloalkenones: Regiospecific syntheses of dienones and allenes

Menyan Cheng, Martin Hulce

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

To investigate the preparation of allenes by means of 1,6-addition reactions to 2-alken-4-ynones, 3-ethynyl-2-cycloalkenones (5) were synthesized and reacted with a variety of organocopper nucleophiles. Such nucleophiles undergo regiospecific 1,6-additions to generate intermediate allenyl enolates (10), which are regiospecifically and stereoselectively protonated to yield a preponderance of (Z)-3-alkenyl-2-cycloalkenones (6-8). The reaction is sensitive to the nature of the organocopper reagent used; higher order cyanocuprates derived from organolithium reagents are the reagents of choice. The intermediate allenyl enolates (10) can be trapped as their enol triflates (13), which in turn can be converted into enallenes (14). Non-organocopper nucleophiles also can add to the terminal carbon of the alkynyl moiety of the enynones studied, but the mechanism may be distinct from that of 1,6-addition: (phenylthio)lithium adds to 3-ethynyl-2-methyl-2-cyclopentenone (5a) by a syn-carbometalation-like mechanism and upon protic quenching yields a preponderance of (E)-2-methyl-3-(2-(phenylthio)ethenyl)-2-cyclopentenone (6h).

Original languageEnglish
Pages (from-to)964-975
Number of pages12
JournalJournal of Organic Chemistry
Volume55
Issue number3
StatePublished - 1990
Externally publishedYes

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Nucleophiles
Addition reactions
Lithium
Quenching
Carbon
propadiene
cyclopentenone

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

Cite this

1,6-Addition of organocopper reagents to 3-alkynyl-2-cycloalkenones : Regiospecific syntheses of dienones and allenes. / Cheng, Menyan; Hulce, Martin.

In: Journal of Organic Chemistry, Vol. 55, No. 3, 1990, p. 964-975.

Research output: Contribution to journalArticle

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