Additions Michael-type, nitromethane

The most recent entry to bicyclic P-lactam compounds through this approach, has been introduced by Barrett and his coworkers [120] by using an intramolecular Michael type reaction of a Af-silyl p-lactam to a nitroalkene induced by fluoride ion (Scheme 45). Namely, the known P-lactam 299 [32a] readily prepared from CSI addition to 1,5-hexadiene, was protected by using TBDMSCI and DIPEA to produce the p-lactam 300. Subsequent ozonolysis, gave the aldehyde 301. Henry reaction of the aldehyde 301 with (phenylthio)-nitromethane furnished, after dehydration of the resulting nitroaldol, the nitroalkene 302 which smoothly cyclized to the carbapenam 303 in the presence of... 

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 the series for synthesizing dendritic molecules, they prepared various monomers to achieve a directional divergent cascade synthesis. For instance, as shown in Scheme 5, aminotriol 1 was prepared as follows [Eq. (1)] [7] Michael-type addition of nitromethane to acrylonitrile afforded the trisnitrile 2. which was subsequently transformed to the triacid 5. Alternatively, triacid 3 was obtained via a Michael-type addition of nitromethane to methyl acrylate and subsequent hydrolysis of triester 4. Reduction of the acid moieties with di-borane gave nitrotriol 5. Further reduction with Raney nickel yielded the desired aminotriol 1. 

Heterobimetallic asymmetric complexes contain both Bronsted basic and Lewis acidic functionalities. These complexes have been developed by Shibasaki and coworkers and have proved to be highly efficient catalysts for many types of asymmetric reactions, including catalytic asymmetric nitro-aldol reaction (see Section 3.3) and Michael reaction. They have reported that the multifunctional catalyst (f )-LPB [LaK3tris(f )-binaphthoxide] controls the Michael addition of nitromethane to chalcones with >95% ee (Eq. 4.140).205... 

In 2008, Chakraborty el al. reported that Michael addition of nitromethane to the sugar olefinic derivative 36 provided the sugar-based (I-nitro acid ester 37 (Scheme 14), which was used as starting material for the preparation of a novel type of cyclohexyl amines.36... 

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