A convenient synthesis of furopyridine and its 2- and 3-methyl derivatives from ethyl 3-hydroxypicolinate (1) is described.The hydroxy ester 1 was O-alkylated with ethyl bromoacetate or ethyl 2-bromopropionate to give the diester 2a or 2b.Cyclization of compound 2a afforded ethyl 3-hydroxyfuropyridine-2-carboxylate (3) which in turn was hydrolyzed and decarboxylated to give furopyridin-3-(2H)-one (4a).Cyclization of 2b gave the 2-methyl derivative 4b.Reduction of 4a and 4b with sodium borohydride yielded the corresponding hydroxy derivative 5a and 5b respectively, which were dehydrated with phosphoric acid to give furopyridine (6a) and its 2-methyl derivative (6b). 2-Acetylpyridin-3-ol (8) was converted to the ethoxycarbonylmethyl ether (9) by O-alkylation with ethyl bromoacetate, which was cyclized to give 3-methylfuropyridine-2-carboxylic acid (10).Decarboxylation of 10 afforded 3-methylfuropyridine (11).
Shiotani, Shunsaku,Morita, Hiroyuki
p. 665 - 668
(2007/10/02)
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