Search

The addition of triphenylsilyl- or dimethylphenylsilymagnesium bromide to certain chiral 1-acylpyridinium salts affords C-2 silylated dihydro-4-pyridones in good yield and high diastereoselectivity (84 - 96% de). Reduction and substitution reactions of these heterocycles were examined to explore their utility as chiral building blocks. Several highly stereoselective transformations were observed.

Several 2-alkyl-1-phenoxycarbonyl-Δ 3 -piperidines were prepared by the addition of alkylzinc iodides to dihydropyridinium salt (9). The treatment of 4-hydroxy-2-methyl-1-phenoxycarbonyl-1,2,3,4-tetrahydro- pyridine (12) with allyltrimethylsilane in the presence of a variety of Lewis acids was studied and found to give cis- and trans-2-6-dialkyl- Δ 3 -piperidines (14) and (15) in moderate to good yield. Among the Lewis acids studied, stannyl chloride gave the best yield with good stereoselectivity (84:16) favoring the cis-isomer (14). The analogous reaction of the 4-methoxy derivative (13) with organozinc reagents was examined and found to give the cis-isomers (17) as the major products

The asymmetric addition of methyl nucleophiles to homochiral N-acylisoquinolinium salts was studied and utilized in a synthesis of the tetrahydroisoquinoline alkaloid, (+)-carnegine

If sodium methoxide was present as an electrolyte and nacleophile,the 1-acylpyridinium salt intermediate would be deacylated and converted to the free base pyridine.

Reaction de Vilsmeier sur des dihydro-1,2- et -1,4 pyridinecarboxylates-1 de phenyle suivie d'aromatisation par S 8