Henry reaction procedure

A typical Henry reaction procedure using K3PO4 as the base in CHsCN ... 

A typical asymmetric Henry reaction procedure using a chiral copper catalysi ... 

A typical Henry reaction procedure involving lithionitrate and aldehydes and... 

Thus, various kmds of bases are effective in inducing the Henry reaction The choice of base and solvent is not crucial to carry out the Henry reaction of simple nitroalkanes v/ith aldehydes, as summarized in Table 3 1 In general, sterically hindered carbonyl or nitro compounds are less reactive not to give the desired ni tro-aldol products in good yield In such cases, self-condensation of the carbonyl compound is a serious side-reaction Several mochfied procedures for the Henry reaction have been developed... 

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... 

Nitromethylation of aldehydes has been carried out in a one pot procedure consisting of the Henry reaction, acetylation, and reduction with sodium borohydride, which provides a good method for the preparation of l-nitroalkanes.16b 79 It has been improved by several modifications. The initial condensation reaction is accelerated by use of KF and 18-crown-6 in isopropanol. Acetylation is effected with acetic anhydride at 25 °C and 4-dimethylaminopyridine (DMAP) as a catalyst. These mild conditions are compatible with various functional groups which are often... 

The conversion of primary or secondary nitro compounds into aldehydes or ketones is normally accomplished by use of the Nef reaction, which is one of the most important transformations of nitro compounds. Various methods have been introduced forthis transformation (1) treatment of nitronates with acid, (2) oxidation of nitronates, and (3) reduction of nitroalkenes. Although a comprehensive review is available,3 important procedures and improved methods published after this review are presented in this chapter. The Nef reaction after the nitro-aldol (Henry reaction), Michael addition, or Diels-Alder reaction using nitroalkanes or nitroalkenes has been used extensively in organic synthesis of various substrates, including complicated natural products. Some of them are presented in this chapter other examples are presented in the chapters discussing the Henry reaction (Chapter 3), Michael addition (Chapter 4), and Diels-Alder reaction (Chapter 8). 

The base-catalyzed reaction of nitroalkanes and sugar-based aldehydes (the Henry reaction) is one of the most common procedures for the lengthening of the carbon skeleton of a carbohydrate.16 The mild reaction conditions required for the formation of C C bonds by this method are usually compatible with most of the protective groups and masked functionalities involved in multistep synthesis from sugars.17... 

Henry reaction of 1-deoxy-l-nitroaldoses followed by denitration is a valuable strategy to obtain C-glycosyl compounds104 and this procedure was used for the preparation of several C-polysaccharides. 

Both the Henry reaction and the reverse demethylolation are synthetically useful in the chemistry of polynitroaliphatic compounds. The Henry reaction is commonly used to mask the natural chemistry of an aliphatic nitro or terminal em-dinitro group by removing the acidic a -proton(s). In Section 1.7 we discussed the conversion of Q ,ty-dinitroalkanes to their bis-methylol derivatives before subjecting them to oxidative nitration and subsequent demethylolation with base, a procedure which results in the formation of Q ,Q , y, y-tetranitroalkanes. ... 

The Sowden homologation [21], based on the nitroaldol condensation (Henry reaction) [22] between the aldehydo sugar and nitromethane in basic medium, followed by the Nef decomposition [23] of the resultant nitronate in strongly acidic conditions, has been employed in a more limited number of cases than the cyanohydrin synthesis. A recent example in this area is shown by the stepwise homologation of (V-acetyl-D-mannosamine (11) into /V-acetylneuraminic acid (12) [24] (Scheme 4). Also, this procedure has found... 

In this section the synthesis of fluoroalkyl (Section 15.1.4.1.3), a,a-difluoroalkyl (Section 15.1.4.2.3), and trifluoromethyl- and perfluoroalkyl ketones are discussed collectively. The second most widely used method for synthesizing peptide fluoromethyl ketones is the Henry nitro-aldol condensation reaction, which involves the use of (3-nitro alcohols to build the fluoromethyl ketones. As with the modified Dakin-West procedure, the Henry reaction has also been used to synthesize mono-, di-, tri-, and extended fluoromethyl ketones, making it another extremely versatile synthetic method.19 12 19 27 29 33 341 However, similar to the Dakin-West procedure, the products of the Henry reaction are not chiral, since an achiral carbanion is involved in the crucial carbon bond forming step. 

Abstract The possible utilization of room temperature ionic liquids (RTILs), instead of volatile organic compounds (VOCs), in the electrochemical procedures of organic synthesis has been discussed. The synthesis of p-lactams, the activation of carbon dioxide and its utilization as renewable carbon source and the carbon-carbon bond formation reactions via umpolung of aldehydes (benzoin condensation and Stetter reaction) and via Henry reaction have been selected as typical electrochani-cal methodologies. The results, related to procedures performed in RTILs, have been compared with those performed in VOCs. The double role of RTILs, as green solvents and parents of electrogenerated reactive intermediates or catalysts, has been emphasized. 

The need to promote the formation of new carbon-carbon bonds has been always felt in organic chemistry. Therefore, to set up efficient procedures capable to generate these bonds has been considered as the backbone of organic synthesis. Among various carbon-carbon-bond-forming reactions, the benzoin condensation, the S tetter and the Henry reactions are some of the most versatile procedures. 

Significant improvements to the Henry reaction have been achieved by using silyl nitronates and catalytic amounts of fluoride ion or, alternatively, a,a doubly deprotonated primary nitroalkanes. Both of these procedures, discovered by the Seebach group, have proved to be useful for the stereoselective preparation of vicinal amino alcohols. 

When the nitroalkene 125 was subjected to the three-step procedure of Michael addition of propargyl alcohol, Henry reaction, and intramolecular radical cyclization, the Incyclic structure 126 was obtained,... 

Nitrohydroxylated pyrrolidine and piperidine ring systems 1824 have been conveniently obtained by a one-pot procedure involving sequential Michael-Henry reaction between nitroethene and a nitrogen nucleophile 1823 suitably predisposed for the oxidative generation (Swem reaction) of an aldehyde group, which is directly trapped in the subsequent nitroaldolization step [1384]. 

Selectivity in the Fused-Mode Intramolecular [3+2] Cycloadditions of Nitronates The most intensively investigated family of the intramolecular cycloadditions is the fused mode (Scheme 16.32) [76]. In this mode regio-, stereo-, and facial selectivity are completely governed by the tether, which is attached at C(4) of the nitronate. Such nitronates are prepared by [4 + 2] cycloadditions of nitroalkenes that bear the dipolarophile tethered at C(2). These nitroalkenes are typically prepared by a two-step procedure involving Henry reaction followed by dehydration [128]. Selenoxide elimination has been employed in the preparation of a P, 3-disubstituted nitroalkene [90]. Nitronates tethered at C (4) with two-carbon and three-carbon chains coimecting the... 

The 1,6,7-asymmetric induction reaction has also been used to obtain anti aldol adducts. In total synthesis of epi-cochlioquinone A 322, an inhibitor of acyl-CoA cholesterol acyltransferase (Scheme 8.53), adduct 315 was submitted to a one-pot protection-ozonolysis procedure to give aldehyde 316. One-pot Henry reaction-dehydration afforded nitroalkene 317, which was converted into... 

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