α- and α′-Lithiation–Electrophile Trapping of N-Thiopivaloyl and N-tert-Butoxythiocarbonyl α-Substituted Azetidines: Rationalization of the Regiodivergence Using NMR and Computation
摘要:
H-1 NMR and computational analyses provide insight into the regiodivergent (alpha- and alpha'-) lithiation-electrophile trapping of N-thiopivaloyl- and N-(tert-butoxythio-carbonyl)-alpha-alkylazetidines. The magnitudes of the rotation barriers in these azetidines indicate that rotamer interconversions do not occur at the temperature and on the time scale of the lithiations. The NMR and computational studies support the origin of regioselectivity as being thiocarbonyl-directed lithiation from the lowest energy amide-like rotameric forms (cis for N-thiopivaloyl and trans for N-tert-butoxythiocarbonyl).
Lithiation-Electrophilic Substitution of N-Thiopivaloylazetidine
作者:David M. Hodgson、Johannes Kloesges
DOI:10.1002/anie.201000058
日期:2010.4.6
α lithiation and incorporation of diverse electrophiles onto an azetidine ring; in the presence of chiral ligands, this chemistry also provides the first example of an enantioselective electrophilic substitution on a four‐membered ring.
α- and α′-Lithiation–Electrophile Trapping of <i>N</i>-Thiopivaloyl and <i>N</i>-<i>tert</i>-Butoxythiocarbonyl α-Substituted Azetidines: Rationalization of the Regiodivergence Using NMR and Computation
作者:Kelvin E. Jackson、Claire L. Mortimer、Barbara Odell、Jeffrey M. McKenna、Timothy D. W. Claridge、Robert S. Paton、David M. Hodgson
DOI:10.1021/acs.joc.5b01804
日期:2015.10.16
H-1 NMR and computational analyses provide insight into the regiodivergent (alpha- and alpha'-) lithiation-electrophile trapping of N-thiopivaloyl- and N-(tert-butoxythio-carbonyl)-alpha-alkylazetidines. The magnitudes of the rotation barriers in these azetidines indicate that rotamer interconversions do not occur at the temperature and on the time scale of the lithiations. The NMR and computational studies support the origin of regioselectivity as being thiocarbonyl-directed lithiation from the lowest energy amide-like rotameric forms (cis for N-thiopivaloyl and trans for N-tert-butoxythiocarbonyl).