Control of Regioselectivity by the <i>l</i><i>one</i> Substituent through Steric and Electronic Effects in the Nitrosoarene Ene Reaction of Deuterium-Labeled Trisubstituted Alkenes
For the enereaction of 4-nitronitrosobenzene (ArNO) with a variety of primary and secondary lone alkyl-substituted substrates, the twix/twin regioselectivity is constant at about 85:15. In contrast, for the lone tert-butyl group and for lone aryl substituents, the twix regioisomer is obtained exclusively. These regioselectivities have been rationalized in terms of steric interactions and coordination
Direct Cross-Coupling of Allylic C(sp<sup>3</sup>
)−H Bonds with Aryl- and Vinylbromides by Combined Nickel and Visible-Light Catalysis
作者:Long Huang、Magnus Rueping
DOI:10.1002/anie.201805118
日期:2018.8.6
An efficient protocol for the direct allylic C(sp3)−Hbond activation of unactivated tri‐ and tetrasubstituted alkenes and their functionalization with aryl‐ and vinylbromides by nickel and visible‐light photocatalysis has been developed. The method allows C(sp2)−C(sp3) formation under mild reaction conditions with good functional‐group tolerance and excellent regioselectivity.
Enantioselective [2 + 2] Cycloaddition of Unactivated Alkenes with α-Acyloxyacroleins Catalyzed by Chiral Organoammonium Salts
作者:Kazuaki Ishihara、Kazuhiko Nakano
DOI:10.1021/ja073435w
日期:2007.7.1
enantioselective [2 + 2] cycloaddition reaction of unactivatedalkenes with α-acyloxyacroleins to give optically active 1-acyloxycyclobutanecarbaldehydes and subsequent ring expansion to give optically active 2-hydroxycyclopentanone derivatives. Organoammonium salt, H-L-Phe-L-Leu-N(CH2CH2)2-reduced triamine•2.6HNTf2, is a highly effective chiral catalyst for the above enantioselective [2 + 2] cycloaddition. Thus
cross-coupling of alkylhalides with alkenylzinc reagents is described. Primary and secondary alkyl chlorides, bromides, and iodides take part in the reaction to give the corresponding olefins in good to excellent yields in a stereospecific manner. High functional group compatibility is also demonstrated by using combinations of substrates possessing rather reactivesubstituents.
Ironing out the kinks: Efficientnew catalytic systems based on iron thiolates are described for the iron‐catalyzed cross‐coupling of alkyl Grignard reagents with alkenylhalides (see scheme). The reaction is highly chemo‐ and stereoselective. With this new procedure, the use of N‐methylpyrrolidone as a co‐solvent is no longer required.