Quantitative Data on the Effects of Alkyl Substituents and Li–O and Li–N Chelation on the Stability of Secondary α-Oxy-Organolithium Compounds
作者:Pablo Monje、Paula Graña、M. Rita Paleo、F. Javier Sardina
DOI:10.1002/chem.200600864
日期:2007.3.5
more sterically hindered organolithiumcompounds. Alkyl groups adversely affect the stability of organolithiumcompounds when attached to the carbon bearing the negative charge, but the extent of this effect is highly dependent on the nature of the rest of the substituents attached to the anionic center. Quantitative data on the stabilization imparted to organolithiumcompounds by Li-O and Li-N chelation
A process for the preparation of a compound of the formula ##STR1## which comprises deprotonating a carbamate of the formula ##STR2## in an inert solvent with a selective base, in the presence of a chelate-forming diamine to give a compound of the formula ##STR3## and then reacting III in an inert solvent, either with an achiral electrophile of the formula (IV) or (V) or with an optionally prochiral electrophile of the formula (VI) ##STR4## and in the case in which R.sup.1 represents an electrofugic leaving group, optionally again electrophilically substituted with the formation of an acyl anion and renewed deprotonation, and in a last step, solvolytically removing the protecting group --CO--NR.sup.10 R.sup.11.
Enantioselective α-Arylation of <i>O</i>-Carbamates via Sparteine-Mediated Lithiation and Negishi Cross-Coupling
作者:Titouan Royal、Yann Baumgartner、Olivier Baudoin
DOI:10.1021/acs.orglett.6b03472
日期:2017.1.6
A general and enantioselective arylation of carbamates derived from primary alcohols was developed by combining Hoppe's sparteine-mediated asymmetric lithiation with Negishi cross-coupling. Coupled with Aggarwal's lithiation-borylation sequence, the current method provides a short and divergent access to a variety of enantioenriched secondary and tertiary benzylic alcohols.