Substitution at the α-carbons of α,β-unsaturated carbonyl compounds: anti-Michael addition

Sulfones as Synthetic Linchpins: Transition‐Metal‐Free sp3–sp2 and sp2–sp2 Cross‐Couplings Between Geminal Bis(sulfones) and Organolithium Compounds

“…Because vinyl sulfones are often employed as Michael acceptors, a process that invokes preferential attack at the α carbon may at first seem dubious. In fact, such contra‐Michael additions have been reported with a variety of traditional Michael acceptors . More specifically, a contra‐Michael addition–elimination pathway nearly identical to that of mechanism B (Scheme ) has been invoked on multiple occasions to explain the formation of vinyl ethers when styryl sulfones are treated with alkoxides (Scheme a)…”

“…In fact, such contra-Michael additions have been reported with a varietyo ft raditional Michael acceptors. [54] More specifically,a contra-Michael addition-eliminationp athway nearly identical to that of mechanism B( Scheme 10) has been invoked on multiple occasions to explaint he formation of vinyl ethersw hen styryl sulfones are treated with alkoxides (Scheme 12 a). [55] In theirs tudieso n1 ,3-dipolar cycloadditions with nitrile oxides,C aramella et alc alculated theL UMOo f( E)-methyl styryl sulfonea nd foundt hatt he orbitalc oefficientso ft he carbon atoms a and b to thes ulfone hadn earlyi dentical magnitude (À0.442a nd + 0.436, respectively).…”

Nucleophilic addition to nitroacrylates: application towards the synthesis of 2,3-dehydroamino acids and 2,3-diamino acids

“…1 The regioselectivity of the Michael reaction can be reversed by attaching groups with strongly electronwithdrawing properties at the b-carbon, which leads to the formation of the a-substituted products. 2 It was also predicted, based on the theoretical calculations that methyl 3-nitropropenoate should react with nucleophiles to give a a-substituted adduct. 3 This approach has been employed in the synthesis of aliphatic a-thioacrylates, 4a polyfunctionalized a,b-unsaturated esters 4b and very recently in the uncatalyzed a-addition of amines to b-nitroacrylates.…”

Synthesis of a new series of 2-vinylindoles and their cycloaddition reactivity

“…The Michael reaction is one of the most important and reliable carbon-carbon and carbon-heteroatom bondforming methods in organic synthesis. 25 In addition, this type of reaction has been investigated for the functionalization of indoles. [26][27][28][29][30][31][32][33][34] In fact, our methodology has been used for the synthesis of asymmetric 2-substituted indoles and functionalizations of indole.…”