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Reaction of 5,5-dimethyl-3-pyrazolidinone (1) with 2-indanone (2) gave 5,5-
dimethyl-2-(1H-indenyl-2)-3-pyrazolidinone (3) instead of the expected azom
ethine imine 4. Although reaction of 2 substituted 3-pyrazolidinones with a
cetylenedicarboxylates usually gives ring expansion products, such as 1,2-d
iazepines, treatment of 3 with dialkyl acetylenedicarboxylates (5, R = Me;
6 R = Et) resulted in the formation of rel-(7aR,12aS)-6,7-bis (alkoxycarbon
yl)-3,4-dihydro-4,4-dimethyl-7aH-indano[1,2-b]pyrrolo[1,2-a]pyrimidin-2-one
s (7, R = Me; 9, R = Et) as major products and 3,4-bis(alkoxycarbonyl)-7,7-
dimethyl-2-(indenyl-2)-6,7-dihydro-2H,6H-1,2-diazepin-5-ones (8, R = Me: 10
, R = Et) as minor products.