The totalsynthesis of the piperidine alkaloid isoprosopinine A (1) and an improved synthesis of isoprosopinine B (2) are reported. The key steps were alkylation of the anions of the sulphones (5) and (6) respectively with the common intermediate bromide (4) and the novel reductive cleavage of the sulphonamides (7) and (8) with sodium-amalgam.
Imino Diels–Alder reaction of 2-t-butyldimethylsilyloxycyclohexadiene: isolation of an azabicyclo[2.2.2]octene silyl enol ether adduct
作者:Timothy N. Birkinshaw、Alethea B. Tabor、Andrew B. Holmes、Paul R. Raithby
DOI:10.1039/c39880001601
日期:——
The iminoDiels–Alderreaction of (1) with 2-t-butyldimethylsilyloxycyclohexadiene (2) gave after acidic work-up mainly the bicyclic enolethers (5a)(for which a novel X-ray crystal structure determination is reported) and (5b) together with small amounts of bicyclic ketones (3a,b) and cyclohexenones (4a,b).
Face selectivity of Diels-Alderreaction of diene having the stereogenic center at allylic position depends on dienophile polarity, and hetero Diels-Alderreaction with dienophile such as N-tosylimine and N-tosylsulfinylimine was found to give exclusively ul product. The reaction mechanism and empirical rule of the face selectivity of these reactions are discussed.