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Reaction of phenyllithium with E ‐cinnamaldehyde: survey of several variables and their influence on the mechanism of reaction and in organic synthesis
Author(s) -
Nudelman Norma S.,
Schulz Hernan G.,
García Graciela V.
Publication year - 1998
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(1998100)11:10<722::aid-poc35>3.0.co;2-#
Subject(s) - chemistry , cinnamaldehyde , phenyllithium , mechanism (biology) , organic chemistry , computational chemistry , reaction mechanism , epistemology , catalysis , philosophy
The reaction of phenyllithium (PhLi) with E ‐cinnamaldehyde ( 1 ) has been fully examined. Besides the main product E ‐1,3‐diphenyl‐2‐propen‐1‐ol ( 2 ), three other by‐products were detected: E ‐cinnamyl alcohol ( 3 ), E ‐chalcone ( 4 ) and E ‐1,3‐diphenylpropanone ( 5 ). The effect of several variables on the nature and relative yields of products was examined. In all the solvents studied, the selectivity of the reaction was higher at higher temperatures, probably owing to aggregation effects; at lower temperatures the reaction is slower and the amount of by‐products increases. The addition is complete in 1 h at 0 °C in THF for a [PhLi]:[ 1 ] ratio of 1:1, and longer reaction times have almost no effect, while for the reaction in toluene the amount of by‐products increases when the reaction mixture is allowed to stand. The concentration of the reagents has no important effect on the reaction as long as the ratio is kept equal to 1:1. The influence of light was examined and a marked decrease in the selectivity of the reaction was observed. When the reaction was carried out in the presence of radical traps, no by‐products were detected. Finally, for a [PhLi]:[ 1 ] ratio of 3:1 the main product is the dihydrochalcone 5 , especially for long reaction times. All the above results could be interpreted in a reaction scheme involving electron transfer from PhLi to 1 , and further reaction of the radical ions formed as well as reaction of dimeric PhLi without previous deaggregation when the ratio is 3:1.­© 1998 John Wiley & Sons, Ltd.

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