Synthesis of Nitrogenated Heterocycles by Asymmetric Transfer Hydrogenation of <i>N</i>‑(<i>tert</i>-Butylsulfinyl)haloimines

Highly optically enriched, protected, nitrogenated heterocycles with different ring sizes have been synthesized by a very efficient methodology consisting of the asymmetric transfer hydrogenation of <i>N</i>-(<i>tert</i>-butylsulfinyl)­haloimines followed by treatment with a base to promote an intramolecular nucleophilic substitution process. <i>N</i>-Protected aziridines, pyrrolidines, piperidines, and azepanes bearing aromatic, heteroaromatic, and aliphatic substituents have been obtained in very high yields and diastereomeric ratios up to >99:1. The free heterocycles can be easily obtained by a simple and mild desulfinylation procedure. Both enantiomers of the free heterocycles can be prepared with the same good results by changing the absolute configuration of the sulfur atom of the sulfinyl group

Synthesis of Nitrogenated Heterocycles by Asymmetric Transfer Hydrogenation of <i>N</i>‑(<i>tert</i>-Butylsulfinyl)haloimines

Highly optically enriched, protected, nitrogenated heterocycles with different ring sizes have been synthesized by a very efficient methodology consisting of the asymmetric transfer hydrogenation of <i>N</i>-(<i>tert</i>-butylsulfinyl)­haloimines followed by treatment with a base to promote an intramolecular nucleophilic substitution process. <i>N</i>-Protected aziridines, pyrrolidines, piperidines, and azepanes bearing aromatic, heteroaromatic, and aliphatic substituents have been obtained in very high yields and diastereomeric ratios up to >99:1. The free heterocycles can be easily obtained by a simple and mild desulfinylation procedure. Both enantiomers of the free heterocycles can be prepared with the same good results by changing the absolute configuration of the sulfur atom of the sulfinyl group

Synthesis of Nitrogenated Heterocycles by Asymmetric Transfer Hydrogenation of <i>N</i>‑(<i>tert</i>-Butylsulfinyl)haloimines

Highly optically enriched, protected, nitrogenated heterocycles with different ring sizes have been synthesized by a very efficient methodology consisting of the asymmetric transfer hydrogenation of <i>N</i>-(<i>tert</i>-butylsulfinyl)­haloimines followed by treatment with a base to promote an intramolecular nucleophilic substitution process. <i>N</i>-Protected aziridines, pyrrolidines, piperidines, and azepanes bearing aromatic, heteroaromatic, and aliphatic substituents have been obtained in very high yields and diastereomeric ratios up to >99:1. The free heterocycles can be easily obtained by a simple and mild desulfinylation procedure. Both enantiomers of the free heterocycles can be prepared with the same good results by changing the absolute configuration of the sulfur atom of the sulfinyl group

Synthesis of γ‑, δ‑, and ε‑Lactams by Asymmetric Transfer Hydrogenation of <i>N</i>‑(<i>tert</i>-Butylsulfinyl)iminoesters

Highly enantiomerically enriched γ- and δ-lactams have been prepared by a simple and very efficient procedure that involves the asymmetric transfer hydrogenation of <i>N</i>-(<i>tert</i>-butylsulfinyl)­iminoesters followed by desulfinylation of the nitrogen atom and spontaneous cyclization to the desired lactams during the basic workup procedure. Five- and six-membered ring lactams bearing aromatic, heteroaromatic, and aliphatic substituents have been obtained in very high yields and ee’s up to >99%. A slight modification of the procedure also allowed the preparation of ε-lactams in good yields and very high enantioselectivities. Both enantiomers of the final lactams could be prepared with equal efficiency by changing the absolute configuration of the sulfinyl chiral auxiliary

Microwave-Assisted Solvent-Free Synthesis of Enantiomerically Pure <i>N</i>-(<i>tert</i>-Butylsulfinyl)imines

A simple, environmentally friendly, and very efficient procedure for the synthesis of optically pure <i>N</i>-(<i>tert</i>-butylsulfinyl)­imines has been developed with microwave-promoted condensation of aldehydes and ketones using (<i>R</i>)-2-methylpropane-2-sulfinamide in the presence of Ti­(OEt)₄, under solvent-free conditions. This procedure allows for the preparation of a variety of sulfinyl aldimines with excellent yields and purities in only 10 min, making any further purification of the imines unnecessary. Several sulfinyl ketimines have also been prepared in good yields by extension of the reaction times to 1 h. This methodology has proved to be equally efficient for the synthesis of aromatic, heteroaromatic, and aliphatic <i>N</i>-(<i>tert</i>-butylsulfinyl)­imines. Conventional heating has also been shown to be useful to promote these reactions, especially for the synthesis of aldimines

Synthesis of Allylic Amines by Asymmetric Transfer Hydrogenation of α,β-Unsaturated <i>N</i>‑(<i>tert</i>-Butylsulfinyl)imines

Primary allylic amines with enantiomeric excesses from 97 to >99% were prepared by asymmetric transfer hydrogenation of α,β-unsaturated <i>N</i>-(<i>tert</i>-butyl­sulfinyl)­ketimines followed by removal of the sulfinyl group. The effect caused by different substituents at the CC bond and at the iminic carbon atom on the chemoselectivity of the reduction was studied. The desired enantiomer of the final allylic amine can be synthesized by choosing the sulfinyl group with the appropriate absolute configuration