Synthesis of 4,4,6-trimethyl-8-R-4H-pyrrolo [3,2,1-ij] quinoline-1,2-diones

Abstract

The features of the Stolle reaction in a series of substituted 2,2,4-trimethyl-1,2-bis (tetra) hydroquinoline have been investigated. When carrying out the reaction of oxalyl chloride not with 2,2,4-trimethyl-1,2-dihydroquinoline and 2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline themselves, but with their hydrochlorides we have succeeded in avoiding the side formation of oxalic diamides 2 and increased the yields of pyrrolo[3,2,1-ij]quinoline-1,2-dione 3a-g up to 90%. It has been determined that carrying out the reaction in methylene chloride requires boiling for 1.5-2 h, in carbon tetrachloride it is 40-50 min, and in toluene it is only 20-30 min. It has been found that in the abovementioned conditions methoxy and benzyloxy groups are not hydrolyzed and, thus, the previously unknown 4,4,6-trimethyl-8-R-4H-pyrrolo [3,2,1-ij]quinoline-1,2-diones containing alkoxy, acyloxy and hydroxy groups have been synthesized. When studying the Stolle reaction for bifunctional 6-hydroxy-2,2,4-trimethyl-1,2- dihydroquinoline it has been found that acylation with oxalyl chloride and the subsequent cyclization proceed selectively only by the secondary amine group of the hydroquinoline ring with saving the hydroxyl group. It has been shown that the use of a two-stage modification of the Stolle method for the synthesis of pyrrolo [3,2,1-ij] quinoline-1,2-diones brings no advantages compared to the classical method of direct interaction of the substrates with oxalyl chloride. The structure of the compounds obtained have been confirmed by IR and 1H NMR spectroscopy and elemental analysis.