Issue 12, 1989

Diastereoselective control of enolate alkylation in 2-acyl-2-alkyl-1,3-dithiane 1-oxides

Abstract

Stereochemical control of enolate alkylation in syn(5) and anti(4) acyl dithiane monosulphoxides has been investigated. The substrates were prepared in high yields from 2-substituted dithianes by acylation in two steps via the corresponding aldehydes followed by sulphoxidation. 2-Acyl-2-alkyl1,3-dithiane 1-oxides were readily deprotonated using a variety of bases. The enolates so generated reacted with methyl iodide and other alkylating agents to give diastereoisomeric mixtures of the alkylated products, the ratios observed being dependent upon the relative stereochemistry of the acyl dithiane oxide, the 2-alkyl substituent, and the base, solvent, and temperature used for the reaction. Diastereoselectivities sufficiently high that the minor isomer could not be detected by 1H n.m.r. spectroscopy at 250 MHz have been observed in some cases (Tables 2 and 3), the most selective system being the anti 2-acyl-2-ethyl derivative (4c). The data obtained fall into clear patterns which may be rationalized by proposing chelated chair-form transition states involving interaction of both the enolate and sulphoxide oxygen atoms with the metal counter-ions.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 1, 1989, 2441-2448

Diastereoselective control of enolate alkylation in 2-acyl-2-alkyl-1,3-dithiane 1-oxides

P. C. B. Page, S. S. Klair and D. Westwood, J. Chem. Soc., Perkin Trans. 1, 1989, 2441 DOI: 10.1039/P19890002441

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements