Anomalous Z-isomer content in Wittig reaction products from keto-stabilised ylides with ortho-heteroatom substituted benzaldehydes

TETRAHEDRON LETTERS

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Article

Byrne, Peter A.¹  Higham, Lee J.²  McGovern, Padraic¹  Gilheany, Declan G.¹ 

[1] Natl Univ Ireland Univ Coll Dublin, Sch Chem & Chem Biol, Conway Inst Biomol & Biomed Res, Ctr Synth & Chem Biol, Dublin 4, Ireland

[2] Newcastle Univ, Sch Chem, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England

关键词: Wittig reaction mechanism;    Keto-stabilised phosphonium ylide;    ortho-Substituted benzaldehydes;    Kinetic control in Wittig reactions;    Z-Alkene;    [2+2] Cycloaddition;   

DOI  :  10.1016/j.tetlet.2012.09.123

来源: Elsevier

【 摘 要 】

Wittig reaction products of keto-stabilised ylides with ortho-substituted benzaldehydes are found to show significantly higher than expected Z-alkene content (up to 50%) compared to analogous reactions of the same ylides with benzaldehyde itself. A cooperative effect is seen whereby the unusual Z-content is further augmented if the ylide bears greater steric bulk in the alpha'-position. These results are consistent with our previous observations on reactions of all ylide types with aldehydes bearing a beta-heteroatom. Significantly, the cooperative effect, previously seen only with semi-stabilised ylides, has now been extended to stabilised ylides. Both the anomalous increase in Z-content and the cooperative effect can be rationalised within the [2+2] cycloaddition mechanism of the Wittig reaction. (C) 2012 Elsevier Ltd. All rights reserved.

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