Sulfonic acids activated methylenes

Other Applications. Hydroxylamine-O-sulfonic acid [2950-43-8] h.2is many applications in the area of organic synthesis. The use of this material for organic transformations has been thoroughly reviewed (125,126). The preparation of the acid involves the reaction of hydroxjlamine [5470-11-1] with oleum in the presence of ammonium sulfate [7783-20-2] (127). The acid has found appHcation in the preparation of hydra2ines from amines, aUphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. It is also an important reagent in reductive deamination and specialty nitrile production. 

DEQ DM DTD MAC EO FADA LAB LAS M MBAS MCPEG Lever s diester quat dialkyldimethyl ammonium ditallow dimethylammonium chloride ethylene oxide fatty acid diethanolamide linear alkylbenzene linear alkylbenzene sulfonate R3S1O0.5 methylene blue active substances mono carboxylated PEG... 

This chapter reports on the reactivity of organic carbonates as alkylating agents, with emphasis on the lightest term of the series, DMC. Under both CF and batch conditions, DMC can react with a number of nucleophilic substrates such as phenols, primary amines, sulfones, thiols, and methylene-active derivatives of aryl and aroxy-acetic acids. The mechanistic and synthetic aspects of these processes will be elucidated. 

Other Applications. Hydroxylainine-O-sulfonic acid has many applications in the area of organic synthesis. The acid has found application in the preparation of hydrazines from amines, aliphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. 

The synthetic utility of this base (1) was demonstrated in the preparation of vinyl iodides in high yields from simple ketohydrazones and iodine (Table), a process that normally gives mixtures of vinyl iodides and geminal diiodides if less hindered bases are employed.6 This base has also been used in the elimination of sulfonic acids from the corresponding sulfonates, the alkylation of compounds containing active methylene groups, the conversion of hydrazones to vinyl selenides, and the preparation of esters from sterically hindered acids.4 5... 

This loses one of the carboxylates on heating in the presence of toluene-sulfonic acid to afford the (B-ketoester (82). Reaction of this intermediate with ethylorthoformate then adds a carbon atom to the activated methylene. Heating that compound with cyclopropylamine in effect exchanges the ethoxy group with the amine to afford enamine (84). Treatment 84 with sodium fluoride leads to displacement of one of the ring fluoro groups by the basic nitrogen on the side chain. This step concludes the formation... 

Nitriles have also been obtained recently from active methylene compounds of type 1 by a two-step process. Treatment with the aminal ester 2 (5, 71-73) leads to an enamine (3), which reacts with hydroxylamine-O-sulfonic acid in an aqueous medium to give a nitrile (4). This reaction docs not proceed through an aldehyde,... 

The halogenopurines react with many other nucleophiles including hydrazines, hydrox-ylamine and alkoxyamines, sulfonic acids and thiocyanates, and compounds with active methylene groups such as diethyl malonate furnish appropriate purine derivatives which offer valuable routes to alkyl and substituted alkyl derivatives. Also aryl groups have been substituted for halogen using aryllithiums (63N224). 

Knorrpyrrole synthesis. The reagent reacts with some active methylene compiounds to give products of C-amination. Thus 2,4-dimethyl-3,5-dicarhethoxypyrrole (2) can be prepared in one step by the reaction of hydroxylamine-O-sulfonic acid with ethyl acetoacctate (1). ... 

The commonly encountered acidic functional groups in organic compounds include carboxylic acids, phenols, ammonium ions, alcohols, and thiols. To a lesser extent, sulfonic acids and active methylene compounds (those containing the —CO—CH2—CO— structural moiety) are also encountered. 

Electrochemical biosensors have been divided into two basic types enzyme-based sensor and electrochemical probe-based sensor. Alkaline phosphatase (ALP) and horse radish peroxidase (HRP) have been often employed for enzyme-based biosensors using p-nitrophenyl phosphate (PNP), a-naphtyl phosphate, 3-3, 5,5 -tetramethylbenzidine (TMB) and 2,2 -azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as substrates of electrochemically active species, and ferrocene (Fc) and methylene blue as the electrochemical mediators. In general, enzymatic amplification of electrochemical signals enables highly sensitive detection of analytes. On the other hand, a direct detection of analytes by using electrochemical probes allows a more rapid time-response onto the detector surface and needs no enzymatic reaction. Based on the reason, a direct detection of analytes by using electrochemical probes has been... 

The primary site of electrophilic attack on 5(4//)-oxazolones is at position C-4. The oxazolones are activated by deprotonation. For example, a variety of 2,4-disubstituted-5(4.H)-oxazolones (80) react with l-fluoro-2,4-dinitrobenzene and sodium carbonate to give 2,4,4-trisubstituted products <88CB67>. When the products are refluxed in methanol containing a catalytic amount of p-toluene-sulfonic acid, they rearrange to 1-hydroxyindazoles (81) (Scheme 24). Apparently, under certain conditions the site of electrophilic attack may be diverted to the 2 position <93TL3907>. Methylene chloride solutions of a, -unsaturated aldehydes, ketones, and esters containing a catalytic amount... 

The condensation of aromatic and aliphatic aldehydes with sulfoxide-activated methylenes like phenylsulfmylacetonitriles and phenylsulfmylacetates selectively forms a-sulfinyl-a,3-unsaturated carbonyl compounds (144) with the alkyl or aryl group trans to the sulfinyl group (see Section 1.11.2.5). 2 Oxidations of (144) with m-chloroperbenzoic acid yield the unsaturated ( )-sulfones... 

The nitration of active methylene compounds by the action of a nitrate ester under basic conditions has been found to be a general and convenient method for introducing a nitro group alpha to the activating group. By choosing the appropriate base-solvent system, we have been successful in applying the reaction to ketones, nitriles, amides, carboxyl esters, sulfonic esters, sul-fones, substituted toluenes, and heterocyclics. Usually the nitration under acidic conditions fails with these classes of compounds. 

A difficulty sometimes encountered in the alkylation of active methylene compounds is the formation of unwanted dialkylated products. During the alkylation of the sodium salt of diethylmalonate, the monoalkyl derivative formed initially is in equilibrium with its anion. In ethanol solution, dialkylation does not take place to any appreciable extent because ethanol is sufficiently acidic to reduce the concentration of the anion of the alkyl derivative, but not that of the more acidic diethylmalonate itself, to a very low value. However, replacement of ethanol by an inert solvent favours dialkylation. Dialkylation also becomes a more serious problem with the more acidic cyanoacetic esters and in alkylations with very reactive electrophiles such as allyl or benzyl halides or sulfonates. 

Acrylic acid derivatives as well as a,p-unsaturated nitriles, imides, phosphonates, and sulfones have been also studied as Michael acceptors for activated methylenes. Dixon et al. have demonstrated the efficacy of bifunctional cupreidine 125 (Fig. 2.12)... 

Additional modifications to the Hantzsch 1,4-dihydropyridine synthesis generally involve the use of activated methylene compounds such as 1,3-diketones, co-cyanoacetophenone, co-phenylacetophenone, a, P-unsaturated ketones, and indane-l,3-diones. A number of efforts to improve reaction yields using eatalysts have also been reported, including the use of hydrotalcite materials, triphenylphosphine copper II triflate, and covalently anchored sulfonic acid on silica gel. Dihydropyridine synthesis has also recently been studied with high success using microwave and solvent-free" reaction conditions. 

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