Organometallic reactions of .omega.-heterosubstituted N-acyl lactams. A new route to .gamma.-keto aldehydes from 5-ethoxy-2-pyrrolidinone
作者:Diego Savoia、Vittorio Concialini、Sergio Roffia、Luca Tarsi
DOI:10.1021/jo00005a030
日期:1991.3
A new route to gamma-keto aldehydes has been developed in which 5-ethoxy-2-pyrrolidinone is the key intermediate, easily available from 2-pyrrolidinone or succinimide. The lactam undergoes the selective ring opening, previous ''in situ'' N-acylation reaction with pivaloyl chloride or di-tert-butyl dicarbonate and attack of Grignard reagents or pyridyllithium compounds, whereupon the gamma-keto aldehydes are produced by acidic hydrolysis. By this way the gamma-keto aldehydes, which are precursors of natural compounds, such as dihydrojasmone and methyl dihydrojasmonate, a feromone component of the peach fruit moth Carposina niponensis, and nicotine derivatives have been prepared. A practical synthesis of pyridyl-substituted pyrroles (alpha- and beta-nicotyrine and the nor derivatives) can be achieved without purification of the intermediates. N-Acylated 6-ethoxy-2-piperidinone is less reactive toward the organometallic attack, affording in low yields 5-phenyl-5-oxopentanal using phenylmagnesium chloride, and 2-pentylcyclohex-2-en-1-one using n-hexylmagnesium bromide.