Olefination with phosphorus ylides. I. Mechanism and stereochemistry of the Wittig reaction

Unstabilized P ylides and their betaines added Li salts, losing most of their reactivity, and were reactivated with tert-BuOK, making thus possible the retardation or the acceleration of the Wittig reaction. The C:O olefination often yielded an isomer mixt. contg. .apprx.1:1 cis- and trans-olefins, due to 2 opposite effects. P ylides were condensed with aldehydes, under kinetic control, preferentially into erythro-betaines, and yielded, when the betaine formation was rendered irreversible, mostly cis-olefins. On the other hand, the threo-betaine was thermodynamically more stable, so that the rapid attainment of diastereomeric equil. between erythro- and threo-betaine led mostly to trans-olefins. Preparative methods of the cis or transselective C:O olefination are described. [on SciFinder (R)]

Published in:
Justus Liebigs Annalen der Chemie, 708, 1-35
CAN 68:28913 22 Physical Organic Chemistry Univ. Heidelberg,Heidelberg,Fed. Rep. Ger. Journal 0075-4617 written in German. 767-99-7; 1879-52-3; 7642-04-8; 7642-14-0; 7642-15-1; 7642-19-5 Role: PRP (Properties) (mixt. with (E)-isomer); 768-00-3; 1879-53-4; 13389-42-9; 14850-23-8; 18654-73-4; 18654-74-5 Role: PRP (Properties) (mixt. with (Z)-isomer); 3412-47-3 Role: PRP (Properties) (mixt. with erythro-isomer); 3412-46-2 Role: PRP (Properties) (mixt. with threo-isomer); 764-75-0P; 766-90-5P; 768-49-0P; 873-66-5P; 896-33-3P; 1005-64-7P; 1073-67-2P; 1192-37-6P; 1560-09-4P; 1608-27-1P; 1657-45-0P; 1657-49-4P; 1657-50-7P; 1657-53-0P; 1694-19-5P; 1860-17-9P; 2077-29-4P; 4180-23-8P; 4736-60-1P; 6111-82-6P; 6228-47-3P; 7237-34-5P; 7642-11-7P; 7642-12-8P; 7642-16-2P; 7642-17-3P; 7642-18-4P; 14350-50-6P; 16721-43-0P; 18600-43-6P; 18600-44-7P; 18600-45-8P; 18600-46-9P; 18657-09-5P; 18657-10-8P; 18923-69-8P; 20311-43-7P; 21558-87-2P; 21558-87-2P; 25679-28-1P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. of)

 Record created 2006-03-03, last modified 2018-01-27

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