Michael-induced

Michael additions followed by further Michael additions have become popular reactions and are usually referred to as Michael Michael Induced Ring Closure (MIM1RC) reactions. A three component Michael-Michael-aldol reaction of ketone enolates with acrylates can be achieved, resulting in the formation of six-membered ring compounds with good efficiency and high diastereoselectivites319. 

The Michael induced Ramberg-Backlund reactions gives a mixture of ( )- and (Zy dienes via extrusion of S02 from the episulfone intermediate 57 (equation 55)47. 

The Michael-induced condensation reaction between acrylates and aldehydes is dramatically accelerated by high pressure, cutting the reaction time from several days to a few minutes. ... 

The use of heteroaryl vinyl sulfides and vinyl dithiocarbamates (166) as hetero-Michael addition acceptors has been described. Combined chelating and electron-withdrawing effects were postulated to stabilize the transient anionic species and allow smooth Michael-induced ring closure to produce C-glycosides (167).191... 

Chen, T. B. R. A., Burger, J. J., De Waard, E. R. The Michael induced Ramberg-Backlund olefin synthesis. Tetrahedron Lett. 1977, 4527-4530. 

The synthetic potential of these reactions can be illustrated by their use for the construction of poly-functionalized cyclopentanecarboxylic acids and derivatives (Scheme 25). The Michael-induced... 

Incorporation of deuterium at the vinylic positions of alkenes can be carried out very efficiently by performing the Ramberg-BScklund reaction in D2O. Finally, the recently developed Michael-induced and vinylogous modifications of the Ramberg-Backlund reaction offer useful approaches to conjugated dienes and polyenes. 

The least attractive feature of the Michael-induced Ramberg-BScklund reaction is the absence of any useful stereocontrol where several isomeric products are possible, they are all formed. In fact, both stereoisomers of the ot-chloro sulfone (24) give the same mixture of trienes (26) on treatment with sodium phenylsulfmate. The reaction is presumably most useful if the required isomer can be obtained by equilibration of the complex mixture in a subsequent step. 

Alkyl-3-(styrylsulfonyl)thioureas, obtained in the form of their potassium salt by reaction of styrylsulfonamides with alkyl isothiocyanates and potassium carbonate in refluxing acetone, cyclize in weakly alkaline solution, or thermally upon melting (usually at 130 160 °C) via a Michael-induced ring closure to give AT-alkyl-5-aryl-5,6-dihydro-1,4,2-dithiazin-3-amine 1,1-dioxides l.9,16,I9,31,32... 

Numerous variants of the Ramberg-BScklund reaction exist. The most prevalent are the vinylogous and Michael-induced Ramberg-BScklund reactions. Decarboxy-lative, epoxy-, and tandem Diels-Alder Ramberg-Backlund reactions are also found in the literature. 

In 1977, de Waard at the University of Amsterdam conceived and prosecuted a novel approach that he dubbed the Michael-induced Ramberg-Backlund (MIRB) olefin synthesis. 24,25 The reaction of dienyl sulfone 25 with one equivalent of sodium phenylsulfinate produced the Michael-induced Ramberg-Backlund product 26 in 40% yield. 

The Michael-induced RBR exploits the electrophilic nature of vinyl-substituted sulfones. Upon nucleophilic attack, the alkene double bond migrates to form an episulfone intermediate by displacement of an a-halide fScheme R.12T The product alkene, resulting from subsequent SO2 extrusion, is transposed by one position from the original alkene. The a-halide may... 

The asymmetric synthesis of cyclopropanes has attracted continual efforts in organic synthesis, due to their relevance in natural products and biologically active compounds. The prevalent methods employed include halomethylmetal mediated processes in the presence of chiral auxiliaries/catalysts (Simmons-Smith-type reactions), transition-metal-catalyzed decomposition of diazoalkanes, Michael-induced ring closures, or asymmetric metalations [8-10,46], However, the asymmetric preparation of unfunctionahzed cyclopropanes remains relatively undisclosed. The enantioselective activation of unactivated C-H bonds via transition-metal catalysis is an area of active research in organic chemistry [47-49]. Recently, a few groups investigated the enantioselective synthesis of cyclopropanes by direct functionalization reactions. 

The Michael-induced Ramberg-Backlund reaction has been used as the key step in a sequence for the homologation of head-to-tail linked conjugated isoprenoids (Scheme 84). Alternatively, homologation can be performed using the Cs-synthon (206) (Scheme 85), but yields are only moderate. ... 

The reaction of halogenomethylvinylsulphones with sulphinate anions, termed the Michael-induced Ramberg-Backlund olefin synthesis, represents an interes-... 

Cyclopropanation reaction via Michael-induced ring closure reaction... 

CYCLOPROPANATION REACTION VIA MICHAEL-INDUCED RING CLOSURE REACTION... 

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