Irradiation of terminal aromatic gamma,delta-epoxy ketones with a 450 W UV lamp led to Norrish type II cyclization/semi-pinacol rearrangement cascade reaction which formed the benzocyclobutanones containing a full-carbon quaternary center, whereas irradiation of substituted aromatic gamma,delta-epoxy ketones led to the indanones through a photochemical epoxy rearrangement and 1,5-biradicals cyclization
COPPER CATALYZED HALOGENATON AND REACTION PRODUCTS
申请人:Wisconsin Alumni Research Foundation
公开号:US20140371480A1
公开(公告)日:2014-12-18
A Cu(I)-catalyzed 1,3-halogen migration reaction effectively recycles an activating group by transferring a halogen from an sp
2
to a benzylic carbon with good enantioselectivity and concomitant borylation of the Ar-halo bond. The resulting enantio-enriched benzyl halide can be reacted in the same vessel under a variety of conditions to form an additional carbon-heteroatom or carbon-carbon bond while maintaining high ee. The reaction can be used to efficiently prepare novel compounds and intermediates for the preparation of therapeutics and ligands for catalysis.
Formal asymmetric hydrobromination of styrenes via copper-catalyzed 1,3-halogen migration
作者:R. J. Van Hoveln、S. C. Schmid、M. Tretbar、C. T. Buttke、J. M. Schomaker
DOI:10.1039/c4sc02040e
日期:——
An enantioselective Cu(i)-catalyzed 1,3-halogen migration reaction accomplishes a formal hydrobromination by transferring a bromine activating group from a sp2 carbon to a benzylic carbon in good er and with concomitant borylation of the Ar–Br bond.
Total syntheses of 19-hydroxysarmentogenin and ouabagenin were achieved from a key unsaturated steroidal skeleton in 14 and 15 steps overall, respectively, by employing an unsaturation-functionalization strategy. The key unsaturated intermediate bearing a C19-hydroxy functionality was furnished in only four steps from a Hajos-Parrish ketone ketal through an efficient asymmetric dearomative cyclization
A unprecedented intramolecular [2+2] cycloaddition reaction between allenes and silicon-bearing olefins is presented. This is also the first example of the reagent-controlled regioselective [2+2] cycloaddition of allenes. The products in this work were oil compounds. The crystal sponge method was successfully used to determine their structures.