Henry synthesis

If less chlorine is used, this method gives 1-chloroethyl ethyl ether as main product, which is more easily separated from by-products by distillation than in the case of Henry synthesis (see page 232). Similarly chlorination of tetra-hydrofuran under UV-irradiation at —30° to —40° gives 2-chloro- and 2,5-dichloro-tetrahydrofuran,513 and that of dioxan in CC14 at —5° to —10° gives 2,5-dichlorodioxan.514 However, no definite product was isolated on low-temperature chlorination of diisopropyl ether.515... 

The Henry synthesis gives better yields of purer products if one starts, not from the monomer, but from the polymeric aldehyde, this being produced by passing in HC1 for a short time with ice-salt cooling before the main reaction is carried out.991... 

The following, inter alia, can also be obtained by the Henry synthesis chlo-romethyl methyl ether from formaldehyde,518,993 paraformaldehyde,994 or s-trioxan 995 1-chloroethyl ethyl ether from paraldehyde 531,996 and similarly 1-bromo-992,997 and 1-iodo-alkyl ethers.993... 

A two-step synthesis of indoles from o-nitrobenzaldehydes proceeds by condensation with nitromcthanc followed by reductive cyclization. Like the Leim-gruber Batcho method, the principal application of the reaction is to indoles with only carbocyclic substituents. The forniation of the o,p-dinitrostyrenes is usually done under classical Henry condensation conditions but KF/18-crown-6 in propanol was found to be an advantageous reaction medium for acetoxy-substituted compounds[1]. The o,p-dinitrostyrenes can also be obtained by nitration of p-nitrostyrenes[2]. 

Synthesis of Porous Materials Zeolites, Clays, and Nanostructures, edited by Mario L. Occelli and Henri Kessler Methane and Its Derivatives, Sunggyu Lee... 

The Barton-Zard (BZ) pyrrole synthesis is similar both to the van Leusen pyrrole synthesis that uses Michael acceptors and TosMlC (Section 6.7) and the Montforts pyrrole synthesis using a,P-unsaturated sulfones and alkyl a-isocyanoacetates." An alternative to the use of the reactive nitroalkenes 1 is their in situ generation from P-acetoxy nitroalkanes, which are readily prepared via the Henry reaction between an aldehyde and a nitroalkane followed by acetylation. Examples are shown later. 

The synthesis of cyclic nitroalkenes via nitradon of cyclo ilkenes is sttmmarized in Table 3 3 Acyclic nitro ilkenes are more readily prepared via the Henry reacdon than by nitradon of ilkenes fsee Secdon 3 3 1 ... 

The nitro-dldolredcdon between nitrodlkdnes and carbonyl compounds to yieldfi-nitro alcohols was discovered in 1895 by Henry. Since dien, diis reaction has been used extensively in many important syndieses. In view of its significance, diere are several reviews on die Henry reaction." These reviews cover syndiesis of fi-nitro alcohols and dieir applications in organic synthesis. The most comprehensive review is Ref 3, which summarizes the literature before 1970. More recent reviews are Refs. 4 and 5, which summarize literatures on the Henry reaction published until 1990. 

STEREOSELECTIVE HENRY REACTIONS AND APPLICATIONS TO ORGANIC SYNTHESIS... 

Allylic uitro compounds undergo [3.3 sigmatropic rearrangement to afford rearranged idcohols, as shown in Eq. 7.43 ° and Eq. 7.44. Because the allylic uitro compounds used in these reacdons are readily prepared either by the Henry reacdon or the Michael adchdon, these rs may be usefril in orgardc synthesis. 

An elegant example of sequence of reactions involving the Henry reaction, the Michael reaction, and elimination of HNO is demonstrated in a short synthesis of anthracyclmones. Nitromethane is used to introduce the ClO-gronp simultaneously v/irh the C9-hydroxy group fEq. 7,136. ... 

Benzyl isocyanoacetate is a nsefnl reagent for the preparadon of benzyl 5-nnsnbsdnited pyrrole-2-carboxylates, which are widely used In the synthesis of porphyrins." Ono and coworkers have prepared pyrroles snbsdnited with various snbsdnients at the fi-posidons."" Because the reqidsite fi-nitro acetates for nitroalkenesi are readily available by the Henry... 

Nitro Conifionnds Recent Advances in Synthesis and Chemistry Edited by Henry Feuer and Arnold T. Nielsen... 

Sequential radical cyclizations are also featured in an efficient and clever synthesis of the cedrane framework 83 (see Scheme 15).30 Compound 81, the product of a regioselective Diels-Alder reaction between isoprene (79) and nitroethylene (80), participates in a nitroaldol reaction (Henry reaction) with 5-methyl-4-hexenal in the presence of a basic resin to give 82. Because the nitro group in... 

M.C. Henry et al, Synthesis, Compounding, and Properties of Nitroso Rubbers in P.R. Tarrand, ed, Fluorine Chemistry Reviews 1,... 

Liu A, Neilands JB (1984) Mutational Analysis of Rhodotorulic Acid Synthesis in Rhodotorula philimanae. 58 97-106 Livage J, see Henry M (1991) 77 153-206... 

The condensation of nitro compounds and imines, the so-called aza-Henry or nitro-Mannich reaction, has recently emerged as a powerful tool for the enantioselective synthesis of 1,2-diamines through the intermediate /3-amino nitro compounds. The method is based on the addition of a nitronate ion (a-nitro carbanion), generated from nitroalkanes, to an imine. The addition of a nitronate ion to an imine is thermodynamically disfavored, so that the presence of a protic species or a Lewis acid is required, to activate the imine and/or to quench the adduct. The acidic medium is compatible with the existence of the nitronate anion, as acetic acid and nitromethane have comparable acidities. Moreover, the products are often unstable, either for the reversibility of the addition or for the possible /3-elimination of the nitro group, and the crude products are generally reduced, avoiding purification to give the desired 1,2-diamines. Hence, the nitronate ion is an equivalent of an a-amino carbanion. 

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