PCl3-mediated cyclization: Synthesis at room temperature of N-alkenyl derivatives of perhydro-1,4,5-oxa(and thia)diazepine-3,6-dione and of 6,7-diazaspiro[3.4]octane-5,8-dione

The use of the PCl3/hydrazone/dicarboxylic acid combination can be applied in an efficient one-pot procedure for the synthesis at room temperature of the seven-membered ring compounds, 6 (perhydro-1,4,5-oxadiazepine-3,6-diones) and 7 (perhydro-1,4,5-thiadiazepine-3,6-diones), and of the first reported derivatives of the heterocycle 6,7-diazaspiro[3.4]octane-5,8-dione 8. Compounds 6 and 1, containing an N-alkenyl group, were obtained in good yields using diglycolic and thiadiglycolic acids with PCl3 and methylhydrazone 1, with use of a high concentration (0.5 M) of the reagents. N-alkenyl derivatives 8 were obtained in the same manner using 1,1-cyclobutanedicarboxylic acid. Changing the order of addition of the reagents gave almost identical results. In the case in which the exocyclic double bond can give E,Z-isomers, the exclusive or prevalent formation of the E-isomer was always observed. © 1999 John Wiley & Sons, Inc.