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Lewis Acid Mediated Vinyl‐Transfer Reaction of Alkynes to N ‐Alkylimines by Using the N ‐Alkyl Residue as a Sacrificial Hydrogen Donor
Author(s) -
Malakar Chandi C.,
Stas Sara,
Herrebout Wouter,
Abbaspour Tehrani Kourosch
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201300469
Subject(s) - chemistry , substituent , alkyl , allylic rearrangement , hydride , imine , moiety , medicinal chemistry , lewis acids and bases , catalysis , organic chemistry , polymer chemistry , hydrogen
Abstract A variety of N ‐alkyl‐α,α‐dichloroaldimines were vinylated by terminal acetylenes in the presence of Lewis acids such as In(OTf) 3 or BF 3 ⋅ OEt 2 and hexafluoroisopropanol (HFIP) as an additive. The reaction proceeds at ambient temperature and leads to geometrically pure allylic β,β‐dichloroamines. This approach is complementary to previously reported transition‐metal‐catalyzed vinyl‐transfer methods, which are not applicable to aliphatic imines and are restricted to imines that contain an electron‐withdrawing nitrogen substituent. In the present approach, terminal alkynes were used as a source of the vinyl residue, and the N ‐alkyl moiety of the imine acts as a sacrificial hydrogen donor. The additional advantage of this methodology is the fact that no external toxic or hazardous reducing agents or molecular hydrogen has to be used. This new methodology nicely combines a C(sp 2 )C(sp) bond formation, hydride transfer, and an unusual cleavage of an unactivated CN bond, thereby giving rise to functionalized primary allylic amines. A detailed experimental study supported by DFT calculations of the mechanism has been done.