Studies on the chemistry of<i>O,N</i>- and<i>S,N</i>-containing heterocycles. 16. Investigations on the synthesis of new tricyclic β-lactams<i>via</i>[2+2]cycloaddition reaction
作者:Susanne Pippich、Herbert Bartsch、Thomas Erker
DOI:10.1002/jhet.5570340319
日期:1997.5
Starting from methylthioimidates 1–8 a series of corresponding tricyclic β-lactams was synthesized via [2+2]cycloaddition with ketenes generated in situ from substituted acetyl chlorides. Dependent on the bicyclic starting material and on the substituent of the corresponding acetyl chloride N-acetyl derivatives were obtained as by- or sole products.
Reaction of tricyclic azetidinones 1–5 (azetobenzoxazine, -thiazine, -thiazepine and -azepine derivatives) with trifluoroacetic acid led to bicyclic thioesters 6–13. There is evidence for an intermolecular reaction, a possible mechanism is discussed. The structure of two representative thioesters (8 and 9) was elucidated by different NMR experiments, complete assignments of 1H- and 13C-chemical shifts