Dialkyl amides of L-valine, L-isoleucine, and L-tert-leucine (2) are excellent chiral auxiliaries for the construction of quaternary stereocenters at ambient temperature. Enaminoesters 3, prepared from these auxiliaries 2 and Michael donors 1, undergo a copper-catalyzed asymmetricMichaelreaction with methyl vinyl ketone (MVK, 4) to afford products 5 in 70-90% yield and 90-99% ee (enantiomeric excess)
Iron(iii) catalysis of the Michael reaction of 1,3-dicarbonyl compounds and enones
作者:Jens Christoffers
DOI:10.1039/a700838d
日期:——
Iron(III) chloride hexahydrate catalyses the Michael
reaction of β-dicarbonyl compounds and enones under mild and neutral
conditions with excellent yields and product selectivity.
Fischerindolesynthesis with bicyclic ketones yields regioselectively linear annulated tetracyclic products when starting from ketones with a relative trans configuration. On the other hand, starting materials with a relative cis configuration give exclusively angular annulated indole derivatives. The starting materials were prepared in optically active form in three steps by a sequence of asymmetric
Quaternary stereocenters were constructed with an enantioselectivity of up to 91% ee under aerobic conditions and at ambient temperature in the Michael reaction of beta-dicarbonyl compounds and methyl vinyl ketone with Ni(OAc)(2). 4H(2)O and optically active trans-1,2-diaminocyclohexane as a chiral catalyst.