Deprotonation of β,β-disubstituted α,β-unsaturated amides - Mechanism and stereochemical consequences
Keyword(s):
A detailed study of the lithium dialkylamide induced deprotonation of β,β-disubstituted α,β-unsaturated amides is presented. The preferential γ-Z-deprotonation and stereochemical outcome of substituents on the γ-Z carbon atom are rationalized in terms of a cyclic eight-membered transition state, which is supported by DFT calculations. Analogous deprotonations on cyclohexylidenecarboxamides reveal a delicate balance of the preference for the eight-membered cyclic transition state with the effects of existing substituents on the ring and the intervention of a twist-boat transition state.Key words: dienolate, amide, deprotonation mechanism, transition state, enolization, regioselectivity, stereoselectivity.
Keyword(s):
1970 ◽
Vol 92
(25)
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pp. 7467-7470
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1965 ◽
Vol 87
(24)
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pp. 5752-5756
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1994 ◽
Vol 35
(52)
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pp. 9705-9708
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1982 ◽
pp. 1357
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Keyword(s):
1970 ◽
Vol 92
(23)
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pp. 6927-6931
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