Simple route to 3-(2-indolyl)-1-propanones via a furan recyclization reaction

Synthesis of tetracyclic system of 2,4‐di(tert‐butyl)‐6,7‐dihydrofuro[2′,3′:3,4]cyclohepta[1,2‐b]indole

“…We have used this kind of furan reactivity for the development of new approach to benzannulated heterocyclic compounds 2, such as benzofurans [2], indoles [3], isochromones [4], isoquinolones [5], isochromenes [6], via acid-catalyzed recyclization of 2-(ortho-substituted benzyl)furans 1 (Scheme 1).…”

“…The residue was dissolved in petroleum ether and passed through pad of silica gel. Crystallization from petroleum ether in refrigerator gave 3 …”

Opening of the furan ring in 2-R-amino- 3-furfurylthiophenes by the action of acids

“…The interest in this compound is explained by the fact that it can be regarded as a hetero analog of ortho-aminobenzophenones, which are used as starting compounds in the synthesis of derivatives of indole during the recyclization of benzylfurans [2][3][4]. By replacing the aromatic ketones by the heterocyclic analog it is possible to obtain derivatives of the condensed heterocyclic system thieno [2,3-b]pyrrole.…”

“…As for the aromatic analogs [2,3], we used the N-tosyl-substituted methanes 2a,e for the synthesis of the pyrrole derivative. The reaction of compounds 2a,e with the mixture of acids leads to opening of the furan ring accompanied by secondary cyclization, resulting in the formation of derivatives of thieno [2,3-b]pyrrole 5a,b.…”

Phenylfurylthieno[2,3-b]pyridyl-methanes. synthesis and reactions of the furan ring transformation

“…Depending on the character of substituent X two routes of conversion are possible in principle: 1) closing of the hetero-or carbocycle between the furan and benzene rings with the formation of a product of type B [2,3] or 2) cleavage of the heterocycle and annelation of the benzene nucleus with the formation of a product of type C (Scheme 1). From the second route, named by us "furan ring opening -heterocyclic ring closing" [4], derivatives of benzofuran [5,6], indole [4,7], isochromone [8], isoquinolone [9,10], benzopyran [11], and cinnoline [12] were obtained. In particular, derivatives of indole of type C (Z = NTs) were synthesized by us starting from orthoacylaminoarenes D (Scheme 2), converted through carbinols E into compounds of type A (X = NHTs).…”