Reaction with hexamethylenetetramine

Whereas the above reactions are appHcable to activated aromatics, deactivated aromatics can be formylated by reaction with hexamethylenetetramine in strong acids such as 75% polyphosphoric acid, methanesulfonic acid, or trifluoroacetic acid to give saUcylaldehyde derivatives (117). Formyl fluoride (HCOF) has also been used as formyl a ting agent in the Friedel-Crafts reaction of aromatics (118). Formyl fluoride [1493-02-3] in the presence of BF was found to be an efficient electrophilic formyl a ting agent, giving 53% para-, 43% ortho- and 3.5% meta-tolualdehydes upon formylation of toluene (110). 

SOMMELET REACTION. Preparation of aldehydes from aralkyl or alkyl halides by reaction with hexamethylenetetramine followed by mild hydrolysis of the formed quaternary salt,... 

For example, novolacs are phenolic resins obtained by the condensation of phenol (trifunctional monomer) and formaldehyde (bifunctional monomer), using a stoichiometric excess of phenol so that formaldehyde is completely consumed without leading to gelation. In a second step, instead of directly adding the necessary formaldehyde, the polymer network is formed by reaction with hexamethylenetetramine (a condensation product of formaldehyde and ammonia usually called hexa), through a complex set of chemical reactions (Chapter 2). 

Conversion o f(2)-CHjCI (XE-3()5) to ( l-CH NH, via a Delepine reaction with hexamethylenetetramine (ElMTA) followed bv hvdrolvsis... 

Aryl-4-chloromethylthiazoles (64) undergo the Sommelet reaction with hexamethylenetetramine, affording the aldehydes (66) by way of intermediate quaternary salts (65). ... 

Novolac resins are produced from an excess of phenol (F/P<1) to form linear polymers, as illustrated in structure 2, with molecular weights of 200-5000 and glass-transition temperatures of 45-70°C. In two-stage novolac systems cross-linking is accomplished by reaction with hexamethylenetetramine (hexa), which is prepared from formaldehyde and ammonia and may he considered a latent source of formaldehyde. 

Xylox Resin n Trade name for a family of heat-resistant thermosetting resins made by the condensation of aralkyl ethers and phenols, resulting in hydroxyphenylene-p-xylene prepolymers that can be cured to hard, intractable resins by reaction with hexamethylenetetramine or epoxy compounds. These thermosetting resins have the good qualities of phenolics and epoxies, with superior mechanical and electrical properties at elevated temperatures. 

Primary amines through reaction of alkyl halides with hexamethylenetetramine... 

Reaction of alkyl halides 1 with hexamethylenetetramine 2 (trivial name urotropine) followed by a hydrolysis step, leads to formation of primary amines 3 free of higher substituted amines. This method is called the Delepine reaction, a comparable method is the Gabriel synthesis. 

An alkyl halide 1 reacts with hexamethylenetetramine 2 to the quaternary ammonium salt 4, which crystallizes from the reaction mixture ... 

Hexamethylenetetramine can serve as a source of ammonia in the reaction with a 2-(haloacet-amido)benzophenone. The intermediate salts 14, which can be isolated, are readily transformed into benzodiazepinones IS in refluxing ethanol (Method C). Selected examples are given.197 198... 

Normally the reaction Is useful for the conversion of alkyl halides to primary amines without concomitant formation of secondary amines.29 Treatment of polymer 17 with hexamethylenetetramine in a mixture of ethanol/THF afforded an insoluble resin. Using diazabicyclooctane (DABCO), we demonstrated that the reaction could be limited to attack by a single nitrogen in a multifunctional amine, so we did not anticipate crosslinking via bis-quat salt formation. Hydrolysis of 2 with anhydrous HC1 in ethanol generated free amino groups as evidenced by a positive ninhydrin test, but quantitative hydrolysis could not be achieved and the product remained insoluble. One would have expected a simple bis-quat to hydrolyse and open the crosslinked structure. 

Part 23 Determination of formaldehyde and hexamethylenetetramine (HMTA) in food simulants In the case of HMTA, it is treated with acid and heated to release formaldehyde. Formaldehyde in simulant is determined colorimetrically by reaction with chromotropic add in the presence of sulfuric acid... 

Other electrophilic substitution reactions on aromatic and heteroaromatic systems are summarized in Scheme 6.143. Friedel-Crafts alkylation of N,N-dimethyl-aniline with squaric acid dichloride was accomplished by heating the two components in dichloromethane at 120 °C in the absence of a Lewis acid catalyst to provide a 23% yield of the 2-aryl-l-chlorocydobut-l-ene-3,4-dione product (Scheme 6.143 a) [281]. Hydrolysis of the monochloride provided a 2-aryl-l-hydroxycyclobut-l-ene-3,4-dione, an inhibitor of protein tyrosine phosphatases [281], Formylation of 4-chloro-3-nitrophenol with hexamethylenetetramine and trifluoroacetic acid (TFA) at 115 °C for 5 h furnished the corresponding benzaldehyde in 43% yield, which was further manipulated into a benzofuran derivative (Scheme 6.143b) [282]. 4-Chloro-5-bromo-pyrazolopyrimidine is an important intermediate in the synthesis of pyrazolopyrimi-dine derivatives showing activity against multiple kinase subfamilies (see also Scheme 6.20) and can be rapidly prepared from 4-chloropyrazolopyrimidine and N-bromosuccinimide (NBS) by microwave irradiation in acetonitrile (Scheme... 

Experiment 6. Reaction with Ammonia.—Of the formaldehyde prepared 10 c.c. are mixed with a small excess of ammonia and the mixture is evaporated in a small glass dish on the water bath. The colourless crystals which remain consist of hexamethylenetetramine (CH2)6N4 (urotropine.) This reaction proceeds quantitatively. It should be so carried out and the result compared with that obtained by titration. 

Sommelet process org chem The preparation of thiophene aldehydes by treatment of thiophene with hexamethylenetetramine.. so-mal ya, pra-s3s ) Sonnenschein s reagent analychem A solution of phosphomolybdicadd that forms a yellow precipitate with alkaloid sulfates. z6n-3n,shTnz r5,a-j3nt) sonocatalysis chem 1. Initiation of a catalytic reaction by irradiation with sound or ultrasound. 2. Use of sound to impart catalytic activity to a chemical compound. san-3-k3 tal-3-s3s)... 

The third way for the synthesis emanates from 2-methylamino-5-chlorobenzophenone (5.1.5), which is acylated by chloracetic acid chloride, forming 2-chloracetylmethylamido-5-chlorbenzophenone (5.1.6). Reaction of this product with hexamethylenetetramine replaces the chlorine atom in the chloracetyl part of the molecule, giving a hexamethyl-enetetramino derivative of 2-aminoacetyhnethylamido-5-chlorbenzophenone, which upon hydrolysis in an hydrochloric acid ethanol solution undergoes cyclocondensation and gives diazepam (5.1.2) [6,7]. 

Lastly, the KA-process (Bachmann process) is based on the reaction between hexamethylenetetramine dinitrate and ammonium nitrate with a small amount of nitric acid in an acetic anhydride solution. The chemical reaction is presented in Reaction 7.15. 

Butlerov, Alexander M.(1828-1886). Russian chemist known for his numerous works in organic chemistry. He discovered formaldehyde in 1859 and studied its reactions with ammonia, including the formation of hexamethylenetetramine Refs l)H.M.Leicester, JChemEduc 17, 203 9 (1940) 2)Walker, Formaldehyde(1953), 2... 

Alkylation of fluoroolefins is probably the most studied reaction of that kind. Different aspects of this process, such as reaction with formaldehyde and hexamethylenetetramine in HF [3], or condensation of halomethanes with fluoroethylenes, catalyzed by AlCl3 [27] have been reviewed. A recent development in this field mostly associated with the introduction of new catalysts, such as SbF5 [7] or aluminum chorofluoride AlClxFy [12], was covered in two other review articles. Here a brief description of some of these reactions is given. 

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