SYNTHESIS OF NEW 1-LAMBDA(5),4-LAMBDA(5)- DIPHOSPHAPENTALENE AND 1-LAMBDA(5),5-LAMBDA(5)-DIPHOSPHAAZULENE SYSTEMS

Bis[bis(dimethylamino)phosphino]acetylene (2a) and two molecules of di methyl- and diethyl-acetylenedicarboxylate (1a/1b) react in a criss-cr oss-cycloaddition to yield 1 lambda(5),4 lambda(5)-diphosphapentalenes (3), which react further with 1 to yield a 1 lambda(5),4 lambda(5)-di phosphaazulenes (5). A mechanism of both reactions is proposed. The re action of 1 lambda(5),4 lambda(5)-diphosphaazulene with 1a at high pre ssure yields ycarbonyl)-2-[1,2,2tris(methoxycarbonyl)ethenyl]-1 lambda (5),4 lambda(5)-diphosphaazulene (7). The reaction of bis(diphenylphos phino)acetylene (2c) with 1a yields thoxycarbonylethinyl)-3,3,7,7-tetr aphenyl)-2-oxa-3 lambda(5),7 -c,d]azulene-4,5,5a,6,8,9-hexakis(methoxy carbonyl) (9) and phoryl)-5-[1,2-bis-(methoxycarbonyl)-ethylidene]-1 l ambda(5)-phosphol-2,3-bis (methoxycarbonyl) (10).