Acid Catalyzed Reactions of Substituted Salicylaldehydes with 2-Methylfuran

Abstract

Data, concerning condensation reactions of salicylaldehydes and 2-methylfuran are generalized. During the course of investigation a sequence of proceeding transformations is established. It is shown that it is possible to obtain 2-hydroxyarylbis(5-methylfur-2-yl)methane, benzofuran or oxazulene derivatives selectively by simple changing of the reaction conditions.

Furan ring opening ‐ indole ring closure: Synthesis of furo[2′,3′:3,4]‐cyclohepta[1,2‐b]indolium chlorides

“…A similar transformation was observed earlier under the treatment of 2-hydroxybenzylfurans with excess of perchloric acid [20] 2-Acetylaminobenzylfurans 5, which are starting compounds for preparation of the salts 6, can be prepared also by condensation of 2-methylfuran with corresponding 2-acetylaminobenzaldehydes in the presence of an acidic catalyst. We supposed that the conditions of the recyclization (gaseous hydrogen chloride/methanol) are suitable for the preparation of the salts 6 directly from the aldehydes 11 and 2-methylfuran without the isolation of the intermediate compounds 5.…”

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

“…At the same time, it was found earlier that reactivity of (2-hydroxyphenyl)-bis(5-methyl-2-furyl)methanes toward acids is similar to that of (2-aminophenyl)bis(5-methyl-2-furyl)methanes [8,9]. Therefore, it would be interesting to study POCl 3 -induced recyclization of (2-hydroxyphenyl)bis(5-tertbutyl-2-furyl)methanes for comparison with the results obtained for recyclizations of 12 and 13.…”

“…In contrast, similar benzofuran-and indole-based tetracyclic compounds are unstable under the reaction conditions. These substances disproportionate resulting in the corresponding tropylium salts 4 easily (Scheme 1) [8,9].…”

Furyl(aryl)alkanes and Their Derivatives. 19. Synthesis of Benzofuran Derivatives via 2-Hydroxyaryl-R-(5-methylfur-2-yl)methanes. Reaction of Furan Ring Opening - Benzofuran Ring Closure Type

“…In a molecule that contains a smaller furan cycle, this angle is 18°, and in a molecule 3e with a larger phenyl cycle, this angle is 40°. (1) 2750 (2) 5797 (1) 4448 (1) 47 (1) * O (2) 3568 (3) 4516 (1) 8262 (2) 82 (1) * C (1) 650 (3) 6537 (1) 4561 (2) 39 (1) * C (2) -128 (4) 7038 (1) 4135 (2) 48 (1) * C (3) 593 (5) 7253 (1) 3055 (2) 58 (1) * C (4) 2105 (5) 6985 (1) 2408 (3) 59 (1) * C (5) 2914 (5) 6490 (1) 2817 (2) 53 (1) * C (6) 2145 (4) 6279 (1) 3873 (2) 42 (1) * C (7) 1668 (4) 5760 (1) 5520 (2) 40 (1) * C (8) 387 (3) 6190 (1) 5646 (2) 37 (1) 7478 (6) 4776 …”

“…The latter compounds can serve as precursors for benzo [b]furo [2,3-h]-1-oxazulenium salts B both by trityl perchlorate oxidation [4] and by disproportionation in the presence of perchloric acid [5]: Previous results were summarized in review [6]. In the present work we attempt to extend the scope of such reactions.…”