Diastereoselective synthesis of fused oxazolidines and highly substituted 1H-pyrrolo [2,1-c][1,4] oxazines via C–H functionalization

Abstract

The first one pot protocol for the diastereoselective synthesis of oxazolo[2,3-c]isoquinoline was achieved by metal-free, benzoic acid catalyzed reactions under mild conditions via C–H, C–O bond functionalization.

Construction of 1,3-Oxazolidines through a Three-Component [3+2] Cycloaddition of Tetrahydroisoquinolines, Aldehydes, and Ethyl Ketomalonate

“…One equivalent of pyridine-2-carbaldehyde reacted with THIQ to give the azomethine ylide, and the subsequent cycloaddition with another equivalent of the aldehyde afforded the dipyridyl oxazolo­[2,3- a ]­tetrahydroisoquinoline . Recently, Houk and Seidel, Mantelingu, and Rangappa also described the similar results, respectively. However, when the two different carbonyl compounds such as an aldehyde and a ketone exist simultaneously in the reaction system, the problem of how to improve the chemoselectivity of the reaction is still challenging and has rarely been addressed (Figure C).…”

Catalyst‐/Additive‐Free One‐Pot Synthesis of Oxazolidines in Water via Regioselective and Stereoselective C−H Functionalization Approach

“…Based on the control experiments and literature reports [43,44] we depicted a plausible mechanism for the reaction (Scheme 4). First THIQ molecule reacts with aldehyde to give iminium ion [ C ] with the help of solvent water molecule.…”

“…Based on the control experiments and literature reports [43,44] we depicted a plausible mechanism for the reaction (Scheme 4). is not probably formed due to the absence of adjacent benzene ring.…”

“…Kumar et al. synthesized tetrahydroisoquinoline fused oxazolidine by using metal‐free additive benzoic acid in the presence of molecular sieves in CH 3 CN at 50 °C [44] . Seidel and co‐workers reported the formation of one such oxazolidine as side product during the synthesis of 1,3‐oxazine.…”

“…[43] Kumar et al synthesized tetrahydroisoquinoline fused oxazolidine by using metalfree additive benzoic acid in the presence of molecular sieves in CH 3 CN at 50 °C. [44] Seidel and co-workers reported the formation of one such oxazolidine as side product during the synthesis of 1,3-oxazine. They performed the reaction in toluene solvent in the presence of additive benzoic acid and molecular sieves at room temperature and isolated poor yield of diastereomeric mixture of oxazolidine.…”