Ck. Ghosh et S. Sahana, BENZOPYRANS .34. REACTIONS OF 3-SUBSTITUTED 1-BENZOPYRAN-4-ONE WITH N-PHENACYLPYRIDINIUM BROMIDE, Indian journal of chemistry. Sect. B: organic chemistry, including medical chemistry, 35(3), 1996, pp. 203-206
N-Phenacylpyridinium bromide in the presence of potassium carbonate gi
ves the indolizine 10 and pyridinium salt 12 with the aldehyde 1 as we
ll as the acid 2, azirine 14 with the nitrile 3, and zwitterion 16 wit
h the ester 4. The pyridinium bromide 12 is converted into 10, and a m
ixture of 5 and 10 on refluxing in pyridine and dimethylformamide, res
pectively.