- 1-Acyl-4-alkylidene-1,4-dihydropyridines, 7. Activation with Boron Trifluoride: Intermolecular Acyl Group Transfer and Formation of 1-(4-Pyridyl)-2-alkanones
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1-Acyl-4-alkylidene-1,4-dihydropyridines 5, representatives of the thermally stable enamides, can be activated by means of boron trifluoride 6, so the ketones 7 result from attack of 6 on 5 (intermolecular acyl group transfer).The mechanism of this reaction, which has not previously been observed for enamides, is strongly suggested to be as follows: 5 and 6 form first the adduct 21, which attacks 5 with formation of 27.Special examples of 5 (11 and 12) are found to be reactive enough that the ketone 7h or the sulfone 15 can be obtained from their isolable precursors (14 and 13) without Lewis-acid activation. 13 is particularly noteworthy: being the precursor of the salt 16, which is generated in situ, it serves as an extremely effective tosylating agent.Even tertiary alcohols are attackted by 16.
- Anders, Ernst,Will, Wolfgang,Stankowiak, Achim
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p. 3192 - 3204
(2007/10/02)
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