Regiocontrolled allylic functionalization of internal alkene via selenium-π-acid catalysis guided by boron substitution

Abstract

The selenium-π-acid-catalysis has received increasing attention as a powerful tool for olefin functionalization, but the regioselectivity is often problematic. Reported herein is a selenium-catalyzed regiocontrolled olefin transpositional chlorination and imidation...

Boryl-Dictated Site-Selective Intermolecular Allylic and Propargylic C–H Amination

“…Moving the B­(MIDA) moiety from an α position far away to the β position, a dramatic decrease of regioselectivity (2:1) was observed. The use of 106 , bearing an electron-withdrawing ester group, furnished the amination product with trivial selectivity, indicating that the C–H acidity is not a key factor for selectivity, unlike our recent observation in a C–H chlorination reaction . Moreover, the reaction of prenyl B­(MIDA) delivered the amination product at the terminal methyl group, a similar result to that reported by Michael, indicating the directing effect of B­(MIDA) could not outpace the classic Markovnikov’s rule.…”

“…The use of 106, bearing an electron-withdrawing ester group, furnished the amination product with trivial selectivity, indicating that the C−H acidity is not a key factor for selectivity, unlike our recent observation in a C−H chlorination reaction. 44 Moreover, the reaction of prenyl B(MIDA) delivered the amination product at the terminal methyl group, a similar result to that reported by Michael, 13 indicating the directing effect of B(MIDA) could not outpace the classic Markovnikov's rule. Competition experiments between oct-4-yne and S-19 resulted in preferential formation of allyl α-amino boronate 19 (Scheme 3b), suggesting an activating role of B(MIDA) on the double bond, in line with the reaction outcome of product 38 in Table 2.…”

Recent advances in the synthesis and reactivity of MIDA boronates

“…Recently, the Wang group reported the selenium-catalyzed regiocontrolled olefin transpositional chlorination and imidation reaction of allylic MIDA boronates, which goes via the neighboring electronic stabilizing donation of electron density to boron (Scheme 12(b)). 81 The Wang group also reported a boryl-dictated site-selective intermolecular allylic and propargylic C–H amination to afford α-amino boryl compounds in good yield and high regioselectivity (Scheme 12(c)). 82 Again, the stabilization of the adjacent positive charge by the B(MIDA) group is the key for the stereoselective ene reaction followed by a 2,3-sigmatropic shift to access α-amino MIDA-boron compounds.…”

Electrochemical Selenium-Catalyzed N,O-Difunctionalization of Ynamides: Access to Polysubstituted Oxazoles

“…Selenium catalysis as a significant branch in selenium chemistry has attracted much attention, and considerable progress has been witnessed in this area . Benefitting from the high carbophilicity of selenium catalysts, Se-catalyzed reactions commonly possess some additional advantages such as good functional group compatibility, mild conditions, and excellent selectivity . Hence, selenium catalysts are regarded as an appropriate alternative to transition-metal catalysts for various organic transformations.…”

“…1 Benefitting from the high carbophilicity of selenium catalysts, 1a Se-catalyzed reactions commonly possess some additional advantages such as good functional group compatibility, mild conditions, and excellent selectivity. 2 Hence, selenium catalysts are regarded as an appropriate alternative to transition-metal catalysts for various organic transformations. Since Sharpless pioneering realized the organoselenium-catalyzed allylic chlorination of olefins with N-chlorosuccinimide (NCS) in 1979, 3 organoselenium catalysis has been deeply developed and a diverse range of reliable catalytic strategies for synthetic chemistry have been well-documented.…”