Enantioselective Thiourea-Catalyzed Additions to Oxocarbenium Ions
作者:Sarah E. Reisman、Abigail G. Doyle、Eric N. Jacobsen
DOI:10.1021/ja801514m
日期:2008.6.1
Asymmetric, catalytic reactions of oxocarbeniumions are reported. Simple, chiral urea and thiourea derivatives are shown to catalyze the enantioselective substitution of silyl ketene acetals onto 1-chloroisochromans. A mechanism involving anion binding by the chiral catalyst to generate a reactive oxocarbeniumion is invoked. Catalysts bearing tertiary benzylic amide groups afforded highest enantioselectivities
development of expeditious methods to synthesize these skeletons remains a challenging task. In this work, the catalyticcyclization of biomass-derived 2-furylcarbinols with an azide to form fused triazoles is described. This approach takes advantage of a single catalyst Yb(OTf)3 and operates via a furfuryl-cation-induced intramolecular [3 + 2] cycloaddition/furan ring-opening cascade.
A phosphane‐catalyzed [3+3] annulation of azomethineimines with ynones has been developed. Under mild reaction conditions, the reaction proceeds smoothly to afford tricyclic dinitrogen‐fused heterocyclic compounds in moderate to excellent yields with moderate to excellent stereoselectivies. Using a chiral phosphine as the catalyst, the reaction could work to give the cycloadduct in moderate yield
The first asymmetric decarboxylative [4 + 3] annulation of propargylic carbamates with C, N-cyclic azomethineimines has been developed successfully by a copper- N-heterocyclic carbine system. This strategy led to a series of optically active isoquinoline-fused triazepine derivatives in good yields and with excellent enantio- and diastereoselectivities. Remarkably, Cu-allenylidene intermediates play
Scaffold Diversity through a Branching Double-Annulation Cascade Strategy: Iminium-Induced One-Pot Synthesis of Diverse Fused Tetrahydroisoquinoline Scaffolds
作者:Duddu S. Sharada、Anand H. Shinde、Srilaxmi M. Patel、Shinde Vidyacharan
DOI:10.1021/acs.joc.6b01096
日期:2016.8.5
double-annulation cascade (BDAC) strategy for diverse and complex fused THIQ scaffolds via a highly reactive iminium-induced one-pot double-cyclization sequence involving Pictect–Spengler-type cyclization has been developed for the first time. The salient features of this protocol are that it allows direct and rapid access to unprecedented diversefused THIQ skeletons, is metal/catalyst free, has a