In 2022,Li, Xiaohua; He, Qiuqin; Fan, Renhua published an article in Organic Chemistry Frontiers. The title of the article was 《Divergent synthesis of 4-amino indoles with free amine groups via tandem reaction of 2-alkynylanilines》.Reference of trans-4-Aminocyclohexanol The author mentioned the following in the article:
A process for the divergent synthesis of a variety of 4-amino indoles I [R = Ph, 3-MeC6H4, 4-ClC6H4, etc.; R2 = Me, Et, Ph, etc.; R3 = H, i-Pr, CH2CH2OH, etc.; R4 = H, n-hexyl, cyclopentyl, etc.] having N1 or C4 free amine groups via via tandem reaction of 2-alkynylanilines with amines was reported. This process involved an oxidative dearomatization, an imine exchange, a cascade 1,4-addition/cyclization/aromatization, and a selective deprotection. The formed 4-amino indoles could be converted to 4,7-difunctionalized indoles II [R5 = i-Pr, CH(Me)(Et), CHPh, etc.; R6 = H, C(O)OMe, C(O)OEt; R7 = CH2(2,4-di-MeOC6H3), CH(C(O)Ph)(CH2C(O)Ph), CH(Ph)(OH)(CF3), etc.] via selective Friedel-Crafts alkylation. After reading the article, we found that the author used trans-4-Aminocyclohexanol(cas: 27489-62-9Reference of trans-4-Aminocyclohexanol)
trans-4-Aminocyclohexanol(cas: 27489-62-9) belongs to anime. To avoid the problem of multiple alkylation, methods have been devised for “blocking” substitution so that only one alkyl group is introduced. The Gabriel synthesis is one such method; it utilizes phthalimide, C6H4(CO)2NH, whose one acidic hydrogen atom has been removed upon the addition of a base such as KOH to form a salt.Reference of trans-4-Aminocyclohexanol
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