Barton-Kellogg olefination

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The Barton-Kellogg olefination is a name reaction in organic chemistry , which was first published independently in 1970 by Derek HR Barton (1918-1998) and Richard Kellogg. It is a coupling reaction for the synthesis of, in particular, sterically hindered alkenes from thioketones or ketones via a 3,4-didehydro-1,3,4-thiadiazolidine intermediate.

Overview reaction

In the Barton-Kellogg olefination, a thioketone and a diazo compound react in a 1,3-cycloaddition to form a 3,4-didehydro-1,3,4-thiadiazolidine intermediate. This reacts in several reaction steps in the presence of triphenylphosphine to form an alkene.

Overview reaction of the Barton – Kelogg olefination

Instead of the methyl groups , other alkyl groups can also be used.

Reaction mechanism

In the proposed reaction mechanism, a thioketone 1 and a diazoalkane 2 react with one another in a 1,3-cycloaddition in the first step . After a nitrogen molecule has been split off, a thiirane 3 is formed . An attack by a phosphane derivative and subsequent cleavage of R 3 P = S results in the desired alkene 4 .

Mechanism of the Barton-Kelogg olefination

modification

Alternatively, the Barton-Kellogg olefination can also be carried out starting from a ketone. The ketone is reacted with hydrazine and H 2 S to form a 1,3,4-thiadiazolidine. Oxidation with lead (IV) acetate gives the 3,4-didehydro-1,3,4-thiadiazolidine intermediate, which is thermally converted into the alkene in the presence of triphenylphosphine.

See also

Individual evidence

  1. ↑ DHR Barton, BJ Willis: Olefin synthesis by twofold extrusion processes . In: Journal of the Chemical Society D: Chemical Communications . No. 19 , 1970, pp. 1225 , doi : 10.1039 / c29700001225 ( rsc.org [accessed June 26, 2019]).
  2. ↑ Richard M. Kellogg, Siek Wassenaar: Thiocarbonyl ylides. An approach to "tetravalent sulfur" compounds. In: Tetrahedron Letters . tape 11 , no. January 23 , 1970, p. 1987–1990 , doi : 10.1016 / S0040-4039 (01) 98134-1 ( elsevier.com [accessed June 26, 2019]).
  3. ↑ a b c Wang, Zerong (Daniel Zerong): Comprehensive organic name reactions and reagents . John Wiley, Hoboken, NJ 2009, ISBN 978-0-471-70450-8 , pp. 249-253 .
  4. ↑ a b entry on Barton-Kellogg olefination. In: Römpp Online . Georg Thieme Verlag, accessed on July 5, 2019.