Stereo‐ and Chemodivergent NHC‐Promoted Functionalisation of Arylalkylketenes with Chloral
作者:James J. Douglas、Gwydion Churchill、Alexandra M. Z. Slawin、David J. Fox、Andrew D. Smith
DOI:10.1002/chem.201503308
日期:2015.11.9
Stereo‐ and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N‐heterocyclic carbenes, giving selectively either β‐lactones (up to 88:12 dr, up to 94 % ee) or α‐chloroesters (up to 94 % ee). Either 2‐arylsubstitution or an α‐branched iPr alkyl substituent within the ketene favours the chlorination pathway, allowing
Lewis Acid-Promoted Ketene–Alkene [2 + 2] Cycloadditions
作者:Christopher M. Rasik、M. Kevin Brown
DOI:10.1021/ja3103007
日期:2013.2.6
are the first examples of ketene-alkene [2 + 2] cycloadditions promoted by Lewis acids. Notable features of this method include (1) substantial rate acceleration relative to traditional thermal reactions, (2) good diastereoselectivities and yields for the formation of the cyclobutanone products, and (3) inverse diastereoselectivity compared with related thermal cycloadditions for many examples. These
Asymmetric Dimerization of Disubstituted Ketenes Catalyzed by N-Heterocyclic Carbenes
作者:Hui Lv、Yan-Rong Zhang、Xue-Liang Huang、Song Ye
DOI:10.1002/adsc.200800532
日期:——
A series of chiral N-heterocycliccarbenes (NHCs), derived from L-pyrogutamic acid, were found to be efficient catalysts for the asymmetricdimerization of alkylarylketenes to give the corresponding α-quaternary β-alkylidenyl-β-lactones in good yields with up to 97% ee. A chiral NHC with a proximal hydroxy group is superior in comparison with the corresponding NHC with its hydroxy group protected.
An Asymmetric Hetero-Claisen Approach to 3-Alkyl-3-aryloxindoles
作者:Nicolas Duguet、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1021/ol901441t
日期:2009.9.3
The reaction of a chiral N-phenylnitrone derived from Garner's aldehyde with alkylarylketenes generates 3-alkyl-3-aryloxindoles directly in excellent yields and with good to excellent levels of enantioselectivity (up to 90% ee).