Site-specific preparation of 4-substituted-6-fluoro(carboalkoxyl)benzo[b]furans and benzo[b]thiophenes via base-catalyzed cyclization of enyne derivatives

1,3-Dien-5-ynes: Versatile Building Blocks for the Synthesis of Carbo- and Heterocycles

“…3). 78 Although high yields are usually obtained in these reactions, quite harsh conditions are required. The base-mediated cycloaromatization has been applied to the synthesis of the alkaloid tylophorine, 79 coronene derivatives acting as telomerase inhibitors, 80 angular-shaped anthradiselenophenes 81 and naphthodithiophenes 82 with promising optoelectronic applications, thienoacenes 53 and ethene-bridged terthiophenes.…”

“…On the other hand, base-promoted cycloaromatizations are essentially based on alkyne to allene isomerization under basic conditions of 1,3-dien-5-ynes having a CH 2 R group at the triple bond and subsequent 6π-electrocyclization of the generated allene-diene (Scheme ). Thus, Burton reported in 2006 the DABCO-promoted or DBU-catalyzed synthesis of diverse naphthalenes, including fluoro- and alkoxycarbonyl-substituted ones, from the corresponding 1-aryl-1-en-3-ynes (Scheme , eq 1). − He has also extended this methodology to the synthesis of phenanthrenes by cycloaromatization of o -(alkynyl)­biphenyls (Scheme , eq 2) and of benzo­[ b ]­furanes and benzo­[ b ]­thiophenes from 1-heteroaryl-1-en-3-ynes (Scheme , eq 3) . Although high yields are usually obtained in these reactions, quite harsh conditions are required.…”

New Approaches for the Use of Acetoacetanilide in the Synthesis of Thiophenes and Their Fused Derivatives with Anti-Tumor Activity

“…Thiophenes represent many naturally occurring and designed molecules responsible for a diverse range of biological responses [1]- [6] recently; substituted thiophenes [7] [8] are often representing a class of important and well-studied herterocycles [9]. The interest in this kind heterocycles has spread from early dye chemistry [10] to modern drug design [11] biodiagnostics [12], electronic and optoelectronic devices [13], conductivity-based…”

Palladium-Catalyzed Formal (3 + 2) Cycloaddition Reactions of 2-Nitro-1,3-enynes with Vinylaziridines, -epoxides, and -cyclopropanes

“…A cross-metathesis reaction was also successful between 1,3-dien-5-yne 7a and allyltrimethylsilane, providing the desired product 12 in 43% yield (Scheme c). The 1,3-dien-5-yne 8 was found to undergo an interesting base-promoted cycloaromatization reaction when heated in a microwave reactor at 150 °C with DBU, presumably via the allene intermediate 14 , to give the tricyclic benzothiophene compound 13 in 67% yield (Scheme d). Compound 13 was also obtained directly from the diastereoisomeric mixture of 6n / 6n′ in 57% yield under the same basic reaction conditions.…”