Erythrosine B Catalyzed Synthesis of trans-Dihydro-4H-furo[3,2-c]chromen-4-ones through Photocatalytic Dehydrogenative sp 3 C–O Bond Formation

Abstract

A simple and efficient visible-light-induced methodology has been developed for the selective synthesis of dihydro-4H-furo[3,2-c]chromen-4-one derivatives via dehydrogenative coupling reaction. The methodology is highly useful for the synthesis of varieties of dihydro-4H-furo[3,2-c]chromen-4-ones from readily accessible reactants under oxygen atmosphere. Importantly, the additive-free approach has been also demonstrated for this transformation. The results of the mechanistic investigation showed that this dehydrogenative reaction proceeded through a radical pathway. Additionally, the synthesized dihydro-4H-furo[3,2-c]chromen-4-one has been transformed into different 4H-furo[3,2-c]chromen-4-ones through simple protocols.

Oxone® Mediated Regioselective C(sp2)−H Selenylation and Thiocyanation of Pyrazolo[1,5‐a]pyrimidines at Room Temperature

“…[16] Further this group also demonstrated a photocatalyst-free white-light driven protocol for selenylation of pyrazolo[1,5-a]pyrimidines using potassium peroxodisulfate (K 2 S 2 O 8 ) (Scheme 1c). [17] Re-cently, our group has also elucidated a blue light-mediated direct CÀ H chalcogenation and thiocyanation strategy for 4Hpyrido[1,2-a]pyrimidin-4-ones at room temperature in presence of K 2 S 2 O 8 (Scheme 1d). [18] In this context, we present an investigation detailing the direct C(sp 2 )À H selenylation and thiocyanation of pyrazolo [1,5-a]pyrimidines and other heterocycles effectively achieved at room temperature by employing the bench stable reagent Oxone®.…”

Tunable Regioselective Allylic Alkylation/Iodination of Imidazoheterocycles in Water

“…Few reports are available for direct C–H iodination of imidazoheterocycles employing iodine as an iodinating agent in the presence of either a catalytic zwitterionic salt or stoichiometric amount of tert -butyl hydroperoxide (TBHP) as oxidant under sonication . In continuation of our interest in C–H functionalization, we have developed a simple protocol for the direct C–H allylic alkylation/iodination of imidazoheterocycles employing the combination of allylic alcohol-I 2 (Scheme ). We have demonstrated that the roles of the allylic alcohol and I 2 are interchangeable in these transformations.…”

I2-Catalyzed three-component synthesis of 3-selenylated pyrazolo[1,5-a]pyrimidines

“…In the literature, the protocols for the selenylation of pyrazolo[1,5- a ]pyrimidines are very limited. 12 Recently, we showed that 3-selenylated pyrazolo[1,5- a ]pyrimidines could be synthesized through photocatalytic selenylation of pyrazolo[1,5- a ]pyrimidines. In continuation of our interest in the synthesis of functionalized pyrazolo[1,5- a ]pyrimidines, 12,13 herein we report a three-component approach towards the synthesis of 3-selenylated pyrazolo[1,5- a ]pyrimidines employing amino pyrazoles, chalcones/enaminones and diaryl/dialkyl diselenides (Scheme 1).…”

“…12 Recently, we showed that 3-selenylated pyrazolo[1,5- a ]pyrimidines could be synthesized through photocatalytic selenylation of pyrazolo[1,5- a ]pyrimidines. In continuation of our interest in the synthesis of functionalized pyrazolo[1,5- a ]pyrimidines, 12,13 herein we report a three-component approach towards the synthesis of 3-selenylated pyrazolo[1,5- a ]pyrimidines employing amino pyrazoles, chalcones/enaminones and diaryl/dialkyl diselenides (Scheme 1). This multi-component strategy is more convenient than the previously reported one as it avoids the extraction and purification of pyrazolo[1,5- a ]pyrimidines.…”