Recent Progress in Steroid Synthesis Triggered by the Emergence of New Catalytic Methods

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154510/1/ejoc201901466_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154510/2/ejoc201901466.pd

Oxidative homodimerization of substituted olefins by DDQ visible light photocatalysis

A visible-light-mediated dehydrogenative homocoupling reaction of readily available mono- and disubstituted olefins to afford symmetrical di- and tetrasubstituted buta-1,3-dienes in the presence of catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has been developed. The reaction proceeds for a wide range of substrates giving buta-1,3-dienes in moderate to good yields. We propose a reaction mechanism involving direct oxidative radical coupling followed by proton and hydrogen atom elimination

Acyclic quaternary centers from asymmetric conjugate addition of alkylzirconium reagents to linear trisubstituted enones

Synthetic methods for the selective formation of all carbon quaternary centres in non-cyclic systems are rare. Here we report highly enantioselective Cu-catalytic asymmetric conjugate addition of alkylzirconium species to twelve different acyclic trisubstituted enones. A variety of sp(3)-hybridized nucleophiles generated by in situ hydrozirconation of alkenes with the Schwartz reagent can be introduced, giving linear products bearing quaternary centres with up to 98% ee. The method is tolerant of several important functional groups and 27 total examples are reported. The method uses a new chiral nonracemic phosphoramidite ligand in a complex with copper triflate as the catalyst. This work allows the straightforward stereocontrolled formation of a valuable structural motif using only a catalytic amount of chiral reagent