作者:Fabian Fischer、Daniel Berger、Markus Neuenschwander
DOI:10.1002/(sici)1522-2675(19981007)81:10<1792::aid-hlca1792>3.0.co;2-z
日期:1998.10.7
Various 2-aminopyrylium salts 7 (X = Cl, Br, I) are available in a simple one-pot procedure by reacting 'push-pull' enynes 5 with equivalent amounts of HCl, HBr, or HI. On the other hand, reaction of NF or AcOH with 'push-pull' enynes 5 is considerably slower so that an excess of HF or AcOH I is needed for the reaction to 7 (X = F, AcO). The 2-aminopyrylium salts 7 are the key intermediates in the postulated rearrangement of 5-amino-5-halogeno-pentadienals 6 to 5-halogenopenta-2,3-dienamides 8 (Scheme 1, bottom), which is vinylogous to the well-known rearrangement of 3-amino-3-X-propenals 2 to 3-X-propenamides 3 (Scheme I, top).