Michael-type acceptors

Recently, a rhodium-catalyzed tandem cyclization has been reported with an arylboronic ester bearing a pendant Michael-type acceptor olefin and acetylenic65 or olefinic66 derivatives. This transformation proceeds in a water-containing medium as solvent and proton source. This catalyst system is optimized with electron-rich and bulky ligands to stabilize the rhodium intermediate and decrease the protonolysis of boron derivatives in a protic solvent. 

Nitroglycals65 are excellent Michael-type acceptors,66 where O-, N-, S-, C- and P-nucleophiles can be used as donors.67 An application of this kind of reaction was reported by Schmidt et al. for a new synthesis of 2-deoxy-2-nitro-D-galactose nucleoside 86 and of /V-acetyl-D-galactosamine nucleoside 88, based on addition reactions to 3,4,6-tri-0-benzyl-2-nitro-D-galactal 85 (Scheme 28).68... 

Optically active 2-alkylidene-l,3-dithiane 1,3-dioxides have been prepared as chiral Michael-type acceptors. It was shown that these compounds react under nucleophilic epoxidation conditions to give diastereoselectively the epoxides. Other heteroatom nucleophiles reacted as well <1998JOC7128, 1999PS(153/4)337>. It was further demonstrated that enolates were also effective nucleophiles for the stereoselective addition to 2-alkylidene-l,3-dithiane 1,3-dioxides (Scheme 48) <20050L4013>. 

Hydroacylation of Michael acceptors. The organotetracarbonylferrates obtained by alkylation of disodium tetracarbonylferrate undergo insertion reactions with Michael-type acceptors to give eventually y-keto esters, ketones, and nitriles. The last example shows an interesting synthesis of a cyclopentanone by an intramolecular insertion reaction. ... 

Hydroacylation of Michael-type acceptors is accomplished using organo-tetracarbonylferrates (9), forming 1,4-diones, keto-esters, or keto-nitriles (Scheme 24). ... 

Organotetracarbonylferrates, [RFe(CO)4], continue to find use in organic synthesis. A new synthesis of a-diketones consists of the reaction of aldehydes with alkyl halides and [Fe(CO)s]. The aldehyde, protected as the ethylenedithioacetal, is treated with butyl-lithium and [Fe(CO)s] to generate the acyltetracarbonylferrate (25) which then reacts with the alkyl halide to give the a-diketone in an overall yield of around 60%. [RFe(CO)4] reacts with Michael-type acceptors to give the expected product in about 90% yield [equation (10)]. ... 

A process patent and subsequent publication by Fujita and cowoikers, disclosed an improved, large-scale synthesis of fingohmod. In particular, the problem of competing styrene formation that plagued the original synthesis was addressed. In this approach, a Friedel-Crafts acylation of phenylethyl bromide (8) with octanoyl chloride yielded ketone 9 (Scheme 2). Treatment of ketone 9 with sodium ethoxide affords the expected styrene product (10) however, in this case, styrene 10 can function as a Michael-type acceptor to generate the desired amino malonate product 11 in 55% yield (2 steps). Next, hydrogenolysis of the ketone with palladium on carbon in ethanol provided... 

Alkylideneindolenines 62 found important applications as Michael-type acceptors. Seminal works by Petrini s group [32] documented on the synthesis of 62 via base-assisted decomposition of arenesulfonylalkylindoles 61 (Fig. 5.4a). 

A considerable amount of effort has been devoted to the development of catalytic reactions that use less expensive transition metal catalysts. As an example, the cobalt-catalyzed iodination of activated alkenes has been reported (Scheme 7.115) [144], While only a few examples with Michael-type acceptors were shown, this method has the potential for significant expansion. 

Michael-type acceptors 598 Michaelis-Menten kinetics 880 microwave-assisted organic synthesis (MAOS) 593... 

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