Goffredo Rosini

1.10 – The Henry (Nitroaldol) Reaction

The utilization of carbanions stabilized by various electron-withdrawing groups to effect carbon-carbon bond formation occupies a central position in organic synthesis. This chapter focuses on the reactions of nitro-stabilized carbanions (nitronate anions or their equivalents) with aldehydes and ketones. This route for the coupling of a carbonyl and a nitroalkane component, leading to vicinal nitro alcohols, was discovered in 1895 by Henry1 and is currently known as the Henry or nitroaldol reaction.

Amberlyst 15: A Practical, Mild and Selective Catalyst for Methyl Esterification of Carboxylic Acids.1

Abstract Mild and selective methyl esterification of carboxylic acids are realized using Amberlyst 15 as acid catalyst in methanol. No race mization, epimerization or ketalization products have been observed with this method. Excellent results are obtained in the esterifications of bile acids.

New and efficient synthesis of ω-nitroalcohols and spiroketals by chemio- and regioselective reductive cleavage of 2-nitrocycloalkanones

Abstract ω-Nitroalcohols have been prepared by a new and efficient chemio- and regioselective reductive cleavage performed on 2-nitrocycloketones with sodium borohydride in acetonitrile / water. This reaction opens a more practical and convenient route to the synthesis of spiroketals.

A new route to 1,4 -diketones and its application to (z)-jasmone and dihydrojasmone synthesis

Abstract (Z)-Jasmone ,dihydrojasmone and other 3-methylcyclo=pent-2-en-1-ones are easily synthesized starting from aldehydes and 1-(2-methyl-1,3-dioxolane-2-yl)-2-nitroethane as reagent for 3-ketobutyl anion synthon. Nitro-aldol condensation is the chainlegthening reaction followed by oxidation and denitration via p-toluenesulfonylhydrazones of the corresponding α-nitroke=tones. Removal of protecting groups gives 1,4-diketones which are then cyclized with alkali.

2-(2-Nitroethyl)-1,3-dioxolane as reagent for 3-oxopropyl anion synthon : a new route to jasmonoid and prostaglandin intermediates

Abstract 2-(2-Nitroethyl)-l,3-dioxolane 18 a versatile reagent for 3-oxopropyl anion synthon. New methodology, based on nitro- aldol condensation, oxidation and direct or indirect denitration sequence is developed for the conversion of 2-(2-nitroethyl)-l,3 dioxolane into (Z)-l,4-dioxodec-7-ene, (Z)-2-(2-pentenyl)-2-cy clopenten-l-one, methyl 9,12-dioxododecanoate and methyl 7-(5- oxocyclopentenyl)heptanoate, which are popular Intermediates for syntheses of (Z)-jasmonolds and prostaglandins.

Practical preparation of bicyclo[3.2.0]hept-3-en-6-ones and its utilisation in stereoselective total synthesis of grandisol and lineatin via a versatile intermediate

Abstract New and efficient stereoselective total syntheses have been devised for racemic grandisol and lineatin, two important components of pheromonic blends. They are based on the utilisation of 1,4-dimethylbicyclo[3.2.0]hept-3-en-6-one as a pivotal intermediate. This compound, as well as other bicyclo[3.2.0]hept-3-en-6-ones, are now easily available by a practical bicyclization of the corresponding 3-hydroxy-6-alkenoic acids.

Nitroalkanes as Central Reagents in the Synthesis of Spiroketals

Nitroalkanes can be profitably employed as carbanionic precursors for the assembly of dihydroxy ketone frameworks, suitable for the preparation of spiroketals. The carbon-carbon bond formation is carried out exploiting nitroaldol and Michael reactions, while the nitro to carbonyl conversion (Nef reaction) ensures the correct introduction of the keto group. Several spiroketal systems endowed with considerable biological activity can be prepared using this synthetic strategy.

Kinetic resolution via oxidation of endo-bicyclic octen- and heptenols with Bacillus stearothermophilus

Abstract Kinetic resolution of the racemic endo-bicyclic octenol and heptenols via oxidation with Bacillus stearothermophilus is described. The enantiomerically pure ketones and alcohols can be obtained varying the oxidation time.

Resolution and EPC synthesis of both enantiomers of 2,5-Dimethylbicyclo[3.2.0]heptan-endo-2-ol, Key Intermediate in the Synthesis of Grandisol.

Abstract The pure enantiomers of 2,5-dimethylbicyclo[3.2.0]heptan- endo -2-ol, key intermediate in the synthesis of grandisol, have been conveniently prepared by optiucal resolution with (2S)-(-)- and (2R)-(+)-1-(4-toluenesulphonyl)pyroolidine-2-carboxylic acid chloride (NTP-Cl) as resolving agents, and by an EPC synthesis employing commercially available (3R)-(-)-and (3S)-(+)-linalool as chiral sources.

Linear Aminopolyhydroxylated Structures Through Rapid Domino Assembly of a Highly Functionalized Heterotricyclic System and Its Selective Cleavage

Good selectivity and efficiency is achieved for the formation of heavily functionalized tricyclic systems, obtained in one or two steps from linear, readily available starting materials. The many functionalities assembled on the pivotal tricycle allow different procedures for unfolding it into interesting aminopolyhydroxylated structures in one or two steps (see scheme).