[formula: see text] The influence of catalysts, acid chlorides, and solvents in the acylation of methyl 2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate was studied. Conditions for the regioselective acylation processes were found. Thienopyrrole-based photochrome was synthesized for the first time.

No abstract

Fused pyrrole derivativesFused pyrrole derivatives R 0160 Regioselective Acylation of Methyl 2-Methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate. -The influence of catalysts, acid chlorides and solvents on the acylation of compound (IVa) is studied in detail. The use of AlCl3 allows the regioselective introduction of the acyl group into position 3, whereas the acyl group is introduced into position 6 of thienopyrrole when SnCl4 is used. -(YAROVENKO*, V. N.; SEMENOV, S. L.; ZAVARZIN, I. V.; IGNATENKO, A. V.; KRAYUSHKIN, M. M.; Russ. Chem. Bull. 52 (2003) 2, 451-456; Zelinsky Inst. Org. Chem., Russ. Acad. Sci., Moscow 117913, Russia; Eng.) -M. Paetzel 41-122

We have used the MNDO approximation to carry out a quantum-chemical study showing that the selectivity of acylation of 2-methyl- 4H-thieno[3,2-b]pyrrole-5-carboxylic acid methyl ester under Friedel-Crafts reaction conditions in the presence of AlCl 3 depends more on the electron density distribution in the complexes than on the structure parameters.Thienopyrroles are analogs of indoles and so are of significant interest in synthesis of various bioactive substances. Considerable attention has been focused on designing physiologically active compounds based onConsidering the electron-rich nature of thienopyrroles, electrophilic processes are generally used to modify them. An attractive method for adding functional groups to thienopyrroles is to introduce acyl groups which then can be converted to various functional groups, including heterocyclic moieties. However, a serious and poorly studied problem is how to carry out regioselective reactions with thienopyrroles having free positions on both the thiophene ring and the pyrrole ring.Earlier we showed that in the presence of a two-fold excess of AlCl 3 , acylation of 2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylic methyl ester (1) occurs regioselectively at the 3 position of the diheterocycle, yielding the product 2, while when equimolar amounts of AlCl 3 and thienopyrrole are used, a mixture of 3-and 6-acyl derivatives 2 and 3 is formed (Scheme 1) [4].With the aim of estimating the effect of structural and electronic factors on the selectivity of acylation, in this paper we compare the calculated heats of reaction and the experimentally established percentages of isomers formed, and also the calculated electron density distributions in complexes of thienopyrrole with AlCl 3 and possible routes for electrophilic attack in nonpolar and polar solvents.The calculations were performed using the MOPAC program [5] by the standard semiempirical quantum-chemical method MNDO with full optimization of the geometry for the molecules of thienopyrrole 1, monoketones 2, 3, complexes with aluminum chloride 4-8, and σ-complexes 9, 10 (Scheme 2).

A spectral and kinetic study was carried out of some substituted 1,2 dithienylper fluorocyclopentenes and 1,2 bis(benzo[b]thienyl)perfluorocyclopentenes suitable for use as photosensitive components of photochromic recording media for optical memory. The intro duction of nitro groups into the benzothienyl moieties dramatically decreases photodegradation and increases the fatigue resistance of these photochromes.