Zum Ablauf der Wittig-Reaktion : zyklische oder ringoffene Zwischenstufen ?
| Autor: | Schlosser, Manfred, Piskala, Alois, Tarchini, Claudio, Huynh Ba, Tuong |
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| Předmět: |
Wittig reaction intermediate betaine
oxaphosphetane intermediate Wittig reaction in Wittig reaction intermediates) Kinetics of Wittig reaction (of triphenylphosphonium ylides with benzaldehyde Reaction constant (for Wittig reaction of benzaldehyde) Wittig reaction (intermediates in) Nuclear magnetic resonance (of phosphorus-31 |
| Popis: | Low temp. 31P NMR indicated that the reaction of Ph3P+C-RR1 (I, R = R1 = H, Me) with R2COR3 (R2 = R3 = H; R2 = Ph, R3 = H) under salt free conditions gave the corresponding oxaphosphetane (II); in the presence of Li salts, esp. in Et2O, Ph3P+CRR1CR2R3OLi X- (III) were formed. II (R = Li, R1 = Me, R2 = H, R3 = Ph), formed from II (R = R2 = H, R1 = Me, R3 = Ph) and alkyllithium reagents, rearranged slowly at -78 Deg and rapidly at -20 Deg to give Ph3P+C-MeCH(OLi)Ph. The reaction of I with benzaldehydes had r 1.1 which indicated that the transition states were highly polar and that the ylide acted as a nucleophile. The intermediacy of III in the Wittig reaction and in the formation of the oxaphosphetane was discussed. [on SciFinder (R)] |
| Databáze: | OpenAIRE |
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