Synthesis and Homologation of an Azetidin-2-yl Boronic Ester with α-Lithioalkyl Triisopropylbenzoates
作者:Pascal K. Delany、David M. Hodgson
DOI:10.1021/acs.orglett.9b03901
日期:2019.12.20
loxy organolithiums to give homologated boronicesters that can be further oxidized, homologated, arylated, and deprotected to give a range of α-substituted azetidines. Scalemic α-boryl azetidine-α-triisopropylbenzoyloxy organolithium pairings show stereospecific reagent control, providing access to either diastereomeric series of homologated boronicesters with very high er's.
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).