Stereoselective Alkylations of Chiral Nitro Imine and Nitro Hydrazone Dianions. Synthesis of Enantiomerically Enriched 3-Substituted 1-Nitrocyclohexenes

Abstract

Dianions of chiral nitro imines (generated by a combination of LDA and s-BuLi) underwent diastereoselective alkylation with methyl, butyl, isopropyl, allyl and methallyl iodides. In contrast to the behavior of simple metalloenamines, the most selective auxiliary contained no coordinating groups, but did possess a large steric difference between the two substituents. The yield and selectivity of the alkylations were improved by the addition of HMPA or DMPU. The use of (S)-1-naphthylethylamine as the auxiliary afforded the R absolute configuration of the alkylation products. This stereochemical outcome could be rationalized by simple steric approach controlled alkylation in a conformationally fixed, internally coordinated dianion. A SAMP nitro hydrazone gave poorer yields and selectivities.

The Nitro to Carbonyl Conversion (Nef Reaction): New Perspectives for a Classical Transformation

“…[89] 2-Nitroindole hasapeculiar reactivity since the reduced aromaticity pertaining to the pyrrole unit gives it an itroalkene-like character.R adical induced addition of active methylene compoundst o2 -nitroindole 142 can be carriedo ut using an excess of Mn(OAc) 3 as oxidizing agent (Scheme 47). [90] Because of the acidic conditions,t he obtained adduct 143 is in equilibriumw ith protonated nitronica cid 144 which upon hydrolysis generatesthe alkylideneindanone 145.…”

Additive Free Fe-Catalyzed Conversion of Nitro to Aldehyde under Continuous Flow Module

“…Moreover, Nef has been achieved using aqueous TiCl 4 , SnCl 2 , Fe/HCl, Ru­(bpy) 3 Cl 2 , and Au-TiO 2 and involves a reductive approach that forms oxime as an intermediate. Also, a series of available reports for the Nef reactions proceed via solvolytic methods − depicting the stoichimetry requirement of both base and acid to facilitate this transformation through the formation of nitronate and nitronic acid intermediates, which then are subsequently subjected for the hydrolysis reaction. Biocatalytic conversion of nitro compounds to carbonyl compounds was also achieved by using enzymes. , Other reagents − such as NaNO 2 –AcOH, TBAF-KF, TBAF-MeI, Cs 2 CO 3 –CuCN, DBU or DABCO, NIS-K 2 CO 3 , BF 3 ·OEt 2 , etc.…”