Enantioselective Functionalization of Prochiral Cyclobutanones and Cyclobutenones

Abstract

Enantioselective synthesis of cyclobutane derivatives is still a challenging topic in asymmetric synthesis. [2+2]-Cycloaddition and skeleton rearrangement are two primary strategies to this end. Recently, functionalization of cyclobutanones and cyclobutenones, which are readily available via [2+2]-cycloadditions as prochiral substrates, has emerged as a powerful tool to access versatile four-membered ring compounds. Herein, we summarize some recent advances in these areas from our and other groups.

Catalytic enantioselective synthesis of benzocyclobutenols and cyclobutanols via a sequential reduction/C–H functionalization

“…Several strategies have been developed, including allylic alkylation, 8 -functionalization, 9 conjugate addition 10 and CH functionalization 11 of prochiral or racemic cyclobutane derivatives (Scheme 2a). 12 However, the enantioselective synthesis of chiral benzocyclobutene derivatives is still underdeveloped. 13 Although two efficient palladium-catalyzed CH activation strategies have been developed by Baudoin 14 and Martin 15 groups via similar intermediates five-membered palladacycles, no enantioenriched benzocyclobutene derivative has been prepared by employing the above two methods.…”

Synthesis, Biological Evaluation and Docking Studies of 4H‐[1,2,3] thiadiazolo[4,5‐b]indole Hybrids as Antifungal Agents

“…In recent decades, there has been substantial effort to develop efficient synthetic methods for producing 1,2,3-thiadiazoles. For instance, Kumar and Co. reported the conversion of hydrazones into 1,2,3-thiadiazole in the presence of sulphur oxychloride, [35] Zhang and Co. reported the series of 4,5-disubstituted 1,2,3-Thiadiazole by reacting α -diazo carbonyl compound with carbon disulfide, [36] Hinz and Co. reported the synthesis of 4carbalkoxy-5-thioalkyl-1,2,3-thiadiazole by reacting 1,1-dithiomalonates with p-toluenesulfonyl azide, [37] Chen and Co. reported the synthesis of 1,2,3-thiadiazole by reacting sulphur with acetophenone tosyl hydrazones, [38] Yang and Co. reported the synthesis of 1,2,3-thiadiazole by coupling reaction of enaminones, elemental sulfur, and tosyl hydrazine in the presence of iodine, [39] Lu and Co. synthesise the 1,2,3thiadiazole by coupling thiocyanate salt with N-tosyl hydrazones in the presence of iodine, [40] Shukla and Co. reported the synthesis of 1,2,3-thiadiazoles by electrochemical process from α-phenyl hydrazones, [41] Mo and Co. reported electro-synthesis of 1,2,3-thiadiazole by coupling reaction of elemental sulfur and N-tosyl hydrazones, [42] Zhang and Co. reported the synthesis of 1,2,3-thiadiazole by [4 + 2] and [4 + 1] annulations of azoalkenes, [43] Zhang and Co. reported the synthesis of 1,2,3thiadiazole by coupling 3,4-dichlorothiazoles with hydrazines in presence of external oxidant, [44] Hu and Co. reported the synthesis of 1,2,3-thiadiazoles by reacting sulfonylhydrazones with thionyl chloride, [45] Samdi and Co. reported the synthesis of 1,2,3-thiadiazole by reacting semicarbazones with thionyl chloride. [46] Due to the complicated chemical reactions and toxic oxidants required, these methods were difficult to apply to synthetic processes.…”