Stereoselective Routes to Hexahydropyrroloindoles and Tetrahydropyrroloquinolines from Activated Aziridines and Electron Deficient 3-Indoles.

An unprecedented and novel synthetic route to hexahydropyrrolo[2,3-]indoles bearing -contiguous stereocenters with excellent stereoselectivities (ee of >99%, dr of ≤99:1) has been disclosed that proceeds through the ring opening of activated aziridines with electron deficient 4-substituted indoles followed by a novel cyclization in a domino fashion, thereby obviating the use of 3-substituted indoles as the prerequisite nucleophile. Another efficient synthetic route to tetrahydropyrrolo[4,3,2-]quinolines in excellent yields (≤93%) and excellent enantioselectivity (ee of >99%) has been established via ring opening of activated aziridines with 4-bromo-1-methyl-1-indole at relatively higher temperatures followed by Cu(I)-catalyzed intramolecular C-N cyclization in the same pot. The stability and the formation of products at different temperatures are explained by computational studies.

A synthetic route to 1,4-disubstituted tetrahydro-β-carbolines and tetrahydropyranoindoles via ring-opening/Pictet-Spengler reaction of aziridines and epoxides with indoles/aldehydes.

A simple and efficient synthetic route to various 1,4-disubstituted tetrahydro-β-carbolines and tetrahydropyrano[3,4-b]indoles in high yields and stereoselectivity via LiClO4-catalyzed SN2-type ring opening of aziridines and epoxides with indoles followed by p-toluenesulfonic acid (PTSA) catalyzed Pictet-Spengler reaction is described.

Stereoselective Syntheses of Highly Functionalized Imidazolidines and Oxazolidines via Ring-Opening Cyclization of Activated Aziridines and Epoxides with Amines and Aldehydes.

A mild one-pot stereospecific synthetic route to highly functionalized imidazolidines and oxazolidines via S2-type ring-opening of the corresponding activated aziridines and epoxides with amines followed by -toluenesulfonic acid (PTSA)-catalyzed intramolecular cyclization with aldehydes has been developed. The methodology tolerates a variety of functional groups and furnishes the desired products in high yields (up to 92%) with excellent stereoselectivities (de, ee > 99%). Interestingly, imidazolidines were formed as the cis-isomers, whereas oxazolidines were produced as trans-isomers exclusively.