5-Substituted-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylic acids of the formula ##STR1## wherein: X is hydrogen or lower alkyl; Ar is a moiety selected from the group consisting of ##STR2## in which: Y is oxygen or sulfur; R is hydrogen, methyl, chloro, or bromo, the R substitution being at the 3, 4 or 5 position of the ring; R.sup.1 is hydrogen, lower alkyl, lower alkoxyl, lower alkoxycarbonyl, lower alkylcarbonyl, fluoro, chloro or bromo, the R.sup.1 substitution being at any available position in the ring; R.sup.2 is hydrogen or lower alkyl; are prepared by .beta.-decarboxylation of the corresponding dialkyl-1,1-dicarboxylates. Certain substituted pyrroles are useful as intermediates for preparing the compounds of formula I.
式为##STR1##的5-取代-1,2-二氢-
3H-吡咯并[1,2-a]
吡咯-1-
羧酸,其中:X为氢或较低烷基;Ar为从##STR2##中选择的基团,其中:Y为氧或
硫;R为氢、甲基、
氯或
溴,R取代在环的3、4或5位;R.sup.1为氢、较低烷基、较低烷氧基、较低烷氧羰基、较低烷基羰基、
氟、
氯或
溴,R.sup.1取代在环中的任何可用位置;R.sup.2为氢或较低烷基;通过对应的二烷基-1,1-二
羧酸酯的β-脱羧制备。某些取代
吡咯可用作制备式I化合物的中间体。