Michael donors nitromethane

Later on, the substrate scope of this methodology was extensively explored by Corey s group using the structural analogues 23 and 24 of the above-discussed catalyst 16. A range of Michael donors such as nitromethane [9b] and silyl enolethers [9c] were successfully applied using the catalyst 23 or 24 (Scheme 9.9). In the case where the P-alkyl chalcones 25 with a proton at C(y) were used as acceptors, self-dimerization occurred under PTC conditions to produce the chiral 1,5-dicarbonyl... 

A similar example of a triple Michael/Michael/Aldol reaction has also been developed afterwards, using in this case nitromethane as the initial Michael donor and two equivalents of an a,p-unsaturated aldehyde reagent, which also proceeds with an excellent degree of chemical efficiency and stereocontrol." ... 

There are a couple of examples of cascade processes starting by a Michael-type addition of a carbon nucleophile proceeding under phase-transfer eatalysis conditions which deserve to be mentioned at this point. The first one eonsists of an enantioselective cyclopropanation of 2-bromocyclopentenone by a cascade Michael/intramolecular nucleophilic displacement in which a variety of C-H acidic carbon pro-nucleophiles such as nitromethane, cyanomethylsulfone and benzyl cyanoacetate reacted with this Michael acceptor in the presence of a quinidinium salt of type 67 (Scheme 7.79). In addition, the conditions needed to be optimized for each Michael donor employed, requiring a different catalyst and inorganic base for each case. Under the best conditions, the final cyclopropanes were obtained in moderate yields and enantioselectivities, albeit as single diastereoisomers. 

In 2012, Kudo and coworkers examined the construction of all-carbon quaternary stereocentres via an asymmetric Michael addition, catalysed by resin-supported polypeptide 23. Using a,p-unsaturated aldehydes, comprising a short-chained allq l group in the p-position, and nitromethane as the Michael donor, a series of quaternaiy-carbon containing Michael adducts were synthesised with moderate to good yield (Scheme 13.16) The substitution pattern of the substrates has a vanishingly low impact on the enantioselectivity which was, in all cases, excellent. A further application of... 

Closure of the nonaromatid ring of the anthracycline system has been effected by condensation of a 2-(3-oxobutyl)anthraquinone with nitromethane [135]. After the initial Henry reaction, a Michael-type reaction is induced by the quinone carbonyl in spite of the high electron density of the aromatic ring to be attacked, and the site of attack being a donor. 

Michael addition. Ostaszynski and Wielgat 58] used potassium (luoride as j talysi for the Michael addition of nitromethane to a double bond. (Alkali lorides were originally suggested by Yasuda ct al. [59] as catalysts foi the chael addition reactions.) The work of addition of nitroalkanes was continued J]- Various acceptors, for example, methylacrylate and acrylonitrile, were fd. Among nitroalkanes gem-dinitroalkancs were applied as donors. Nitro-ICS readily formed double salts with KHFj, RbHFj and CsHFj. The yield Ihe adducts of such salts with compounds containing a double bond varied reen 60 and 90%, viz. (5) ... 

In 2002, Itoh and Kanemasa found that the combined use of both amine and chiral Lewis acid (R,R)-DBFOX-Ph complex of Ni(II) can be an active catalyst for enantioselective Michael addition of nitromethane or malononitrile to unsaturated carbonyl compounds [37a,b]. Recently, they have reported a new enol ketone synthesis through the reactions between cyclic 1,3-dicarbonyl donors and a,p-unsaturated carbonyl acceptors under the double catalytic activation conditions (10mol% each) of Ni(11)-perchlorate hexahydrate and (2,2,6,6-tetramethylpiperidine (TMP) (114))(Scheme 16.33) [38a,b]. Thus, 1,3-cyclohexanedione (112) is allowed to react with 4-bromo-l-crotonoyl-3,5-dimethylpyrazole (113), in THF at room temperature in the presence of both catalytic amounts to give 4,7,7-trimethyl-3,4,5,6,7,8-hexahy-drobenzopyran-2(H),5-diones (115) in good yields along with high enantioselectivity up to 99% ee. 

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