Nitromethane condensation, functionalization

Recently, enantioselective organo-catalytic procedures for the aza-Henry reaction have been disclosed. The presence of either an acidic or a basic function appears to be a requisite of the catalyst. In fact, the condensation of ni-tromethane with M-phosphinoyl arylimines 72 is catalyzed by the chiral urea 85 derived from (R,R)-l,2-diaminocyclohexane and gives the product (R)-74 with good yield and moderate enantioselectivity (Scheme 15) [50]. The N-phosphinoyl substituent is determinant, as the addition of nitromethane to the N-phenyl benzaldimine failed and the reaction of the N-tosyl ben-zaldimine gave the expected adduct with quantitative yield but almost no... 

Secondary nitro compounds can be converted into carbanions in similar fashion. Interesting highly functionalized adducts (46) were prepared by addition to levoglucosene (45) (equation 17)59. Mixtures of diastereomeric adducts were generally formed60. The adduct from nitromethane undergoes double Michael addition followed by aldol condensation to afford the novel adduct 47. 

Other flexible molecular models of nitromethane were developed by Politzer et al. [131,132]. In these, parameters for classical force fields that describe intramolecular and intermolecular motion are adjusted at intervals during a condensed phase molecular dynamics simulation until experimental properties are reproduced. In their first study, these authors used quantum-mechanically calculated force constants for an isolated nitromethane molecule for the intramolecular interaction terms. Coulombic interactions were treated using partial charges centered on the nuclei of the atoms, and determined from fitting to the quantum mechanical electrostatic potential surrounding the molecule. After an equilibration trajectory in which the final temperature had been scaled to the desired value (300 K), a cluster of nine molecules was selected for a density function calculation from which... 

MSN materials functionalized with AEP and a hydrophobic secondary group such as allyl (AL) and mercaptopropyl (MP) showed a great polarity effect in the nitroaldol condensation of 4-hydroxy- and 4-octyloxybenzaldehyde with nitromethane (Scheme 3.37). ... 

Nitroalkyl Acids. - Additions of hydrogenphosphinic esters, Ph(R0)P(0)H, or diethyl (lithiodifluoromethyl)phosphonate to nitrostyrene or other nitroalkenes yield the nitroalkyl phosphonates (187) and (188), respectively. Diethyl (lithiodifluoromethyl)phosphonate also, by reaction with DMF, has provided (175), as already noted the condensation between the latter and nitromethane has given a 69% yield of (189) further reactions involving (175) (Scheme 12) have provided several additionally functionalized esters, amongst them (190). 

In several cases, it has been established that the amines do not function as simple bases, but, instead, are involved in prior reaction with the carbonyl compounds as well. Kinetic evidence in support of such a mechanism in the condensation of aromatic aldehydes with nitromethane has been reported. The fact that such condensations are often most effectively catalyzed when a weak acid is present in addition to the amine suggests that amines do not function as simple base catalysts. 

As a result of condensation of 30 with some CH-acids (nitromethane, nitroethane, acetone and malonic acids), also with aniline (scheme 11), were obtained compoimds 54-60 which apart from functional groups contain multiple bond, what gives additional possibility for synthesis of new and interesting compounds from different points of view. 

One year later, Rahaman et al. reported a cascade reaction of aldehyde and nitro alkanes for the synthesis of functionalized y-nitro aldehydes with high reactivity [33], Generation of the intermediate nitro alkenes involved cooperative secondary amine/hydrogen bonding-promoted condensation of nitromethane and aldehydes. Consequently, the newly formed nitro alkenes promptly participated in the next cycle cocatalyzed by the two catalysts (Scheme 9.37). 

Aminopropylated functionalized hexagonal mesoporous silicas (HMS) and SBA-15 materials with different amino-loadings (5-30 wt. % NH ) were synthesized by Pineda et al. (2013). These play important role as catalyst in the microwave-assisted Knoevenagel condensation of cyclohexanone and ethyl cyanoacetate as well as in the Michael reaction between 2-cyclohexen-l-one and nitromethane. The low loaded HMS-5%NH2 and higher loaded SBA-15-20% NH were found to give the best activities in the reactions. High activities and selectivities to the condensation product could be achieved in short times of microwave irradiation for both these base-catalyzed processes. 

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