On the Action of Heat

74BEP819195 75GEP2343462), and decaline (69T4649) have been used. Dowtherm A (b.p. 260°C) is used most widely this is a eutectic mixture of diphenyl ether (73.5%) and biphenyl (26.5%). It is superior to pure diphenyl ether (m.p. 26-27°C) because of its lower freezing point (12°C) (e.g., 46JA1204, 46JA1264). The cyclization can be carried out above 300°C when dibenzylbenzene is used as solvent. 

The volume of solvent used in the cyclization may be varied considerably, depending on the solubility of the aminomethylenemalonate. The purity of the cyclization product is generally higher when the cyclization is carried out at a higher temperature for a shorter reaction period, as 

Raychaudhuri and Basu investigated the formation of side products in the large-scale cyclization of diethyl /V-(3-chlorophenyl)aminomethy-lenemalonate (250) in diphenyl ether (70J1C25). As side products, 7-chloro-1-ethyl-l,4-dihydro-4-oxoquinoline-3-carboxylic acid (551), 7-chloro-4-ethoxyquinoline (552), and 7-chloro-l-ethyl-4(l//)-quinoline (553) could be isolated. These were probably formed from the primarily cyclized product, ethyl 7-chloro-4-hydroxyquinoline-3-carboxylate. The quantities of the side products depended on the reaction temperature during the cyclization, the duration of heating, and the purity of the starting N-(3-chlorophenyl)aminomethylenemalonate (250). 

The cyclized product usually precipitates from the reaction mixture in crystalline form at room temperature. The precipitation of the product may be completed by adding light petroleum, ligroin, or hexane to the reaction mixture (e.g., 51JOC1414 56BRP743901, 56JCS3079). 

Diethyl N,A(-diphenylaminomethylenemalonate (112, R = R1 = H)was heated in diphenyl ether at reflux temperature for I hr to give ethyl 1-phenyl-4-oxo-l,4-dihydroquinoline-3-carboxylate (559) in only 9% yield (69BRP1147336). For other N,/V-diarylaminomethylenemalonates, this procedure was completely unsuccessful. 

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Reaction of pyridinium-A -(2-pyridyl)amidine (402) and alkyl haloace-tates in the presence of K2CO3 afforded a mixture of 4-oxo-4/f-pyrido[l, 2-u]pyrimidine-2-carboxylates 407 and 2-aminopyridine derivatives 406 through intermediers 403- 05, as depicted in Scheme 15 (00TL5837). Compound 406 could be cyclized on the action of heat or silica gel into 407. The best yield was achieved in the case of ethyl bromoacetate. 

Substituted-4-oxo-4//-pyrido[l,2-a]pyrimidines of type 74 (6-R H) are transformed to l,4-dihydro-4-oxo-l,8-naphthyridines on the action of heat.bl)-71-7l, 1 29 1 33 323 325 Ring transformation is facilitated by the nearly coplanar disposition of the 4-CO group and the 6-substituent of the pyrido-[l,2-u]pyrimidines. The steric interaction of these groups is shown by the relatively long C-4—N-5 bond (e.g., 147 pm for ethyl 6-methyl-4-oxo-4/f-pyrido[l,2-u]pyrimidine-3-carboxylate, as determined by X-ray study326). The strain caused by this interaction is relieved when the C-4—N-5 bond cleaves. Ring transformation probably takes place via the reactive imino-ketene intermediate (75).130... 

This intermolecular reaction is reversible, and occurs with certain other nitro compds. [Thermal extraction of the hydroxyl-hydrogen of hydro-quinone by TNT is cited in the section on The Action of Heat (Ref 96)]... 

On the action of heat, trimethylsilyloxiranes are rearranged to silylenol ethers (Eq. 396). "... 

Note on the Action of Heat upon Valeric Acid." Journal of the Chemical... 

In organic chemistry the term refers to compounds containing the NH2 ion or the > NH group. These are prepared by the action of heat on amides or by metathetica reactions in liquid ammonia. The heavy metal imides are explosive. 

Colourless crystals m.p. 174 C. It is obtained by the action of heat on phenyl salicylate. It may be reduced to xanthene. It is the parent substance of the xanthone group of dyestuffs. 

Free-radical initiation of the chain reaction of oxidation can arise from the action of heat, light, metal ions and, sometimes, ozone on a variety of chemical moieties such as those indicated in Table 7.4. 

The Action of Heat.—We will assume in the first 1 ic,. S7. plate that the substance is homogeneous and consists of a single individual. Heat a portion on platinum foil and notice if it volatilises, chars, or burns with a clear, luminous, non-Iuminous (aliphatic), or smoky (aromatic) flame. Determine the nature of the residue, if any, when the carbon has burnt away. 

Undoubtedly these reactions proceed via an intermediate ureido or thioureido derivative. These compounds have been obtained by Dornow and Hahmann by the action of potassium cyanate or ammonium isothiocyanate on 2-amino-4,6-dimethylnicotinic acid (11), but whereas the urea (12, X = 0) was converted into the pyrido[2,3-li]-pyrimidine-2,4(lI/,3/7)-dione (13, X = 0) by the action of heat, the thiourea (12, X = S) was unchanged after similar treatment. 

Camphene is prepared artificially by the isomerisation of pinene with sulphuric acid or by the withdrawal of HCl from pinene monohydrochloride, or by the action of heat in the presence of acetic anhydride on bornylamine, CjjHj7NH2, which causes the withdrawal of ammonia and leaves camphene, as follows —... 

Dipentene, the inactive form of limonene, not only occurs naturally in essential oils, but results by the action of heat on several other ter-penes, and to a considerable extent by the action of sulphuric acid on pinene. 

There are two types of hot feed extruders, one similar to the screw type cold feed extruder, except that the strip feeding the extruder is taken directly off the two-roll mill. The mill is used to further blend and heat the compound. It is then taken off the mill in strip form and fed directly into the extruder. The second type of hot feed extruder is based on the action of a ram being used to feed the compound into the extruder die (Fig. 16). The compound is placed on a two-roll mill to further blend and heat rubber. It is then taken off the mill in pig form to fill the extruder chamber. 

The most important of these are the refractory cements formed by the heat treatment of aluminium acid phosphate solutions. This subject has been well reviewed by Kingery (1950a), Morris et al. (1977), Cassidy (1977) and O Hara, Duga Sheets (1972). The chemistry of these binders is extremely complex as the action of heat on acid phosphates gives rise to polymeric phosphates, with P-O-P linkages, and these are very complex systems (Ray, 1979). 

The action of heat on these cements is complex (Abdelrazig Sharp, 1988). The principal sequence based on XRD and thermal analysis is shown in Figure 6.10. 

Heating 2-(arylaminothiocarbonyl)-T(2-hydroxyethyl)-l,2,3,4-tetrahydroisoquinolines in EtOH in the presence of HC1 afforded 4-arylimino-l,6,7,llb-tetrahydro-2/7,477-[l,3]thiazino[4,3-tf]isoquinolines <2001ARK33>. 1,3,4,6,7,11b-Hexahydro-2/7-pyrimido[6,l-+]isoquinoline-2,4-diones were obtained by the cyclization of 2-(2-aminocarbonyl-l,2,3,4-tetrahydroisoquinolin-l-yl)acetates on the action of a base <2004MOL694>. 

The intramolecular formal [3+3] cycloaddition reaction of l- [l-phenyl-2-(4-oxobut-2-enyloxy)ethyl]amino cyclo-hexen-3-one at 150°C in the presence of piperidinium acetate afforded /ra 3--l,4a-77-l-phenyl-l,2,4,4a,7,8,9,10-octahydro[l,4]oxazino[4,3- ]quinolin-7-one <2002JA10435>. At 85°C, the 6-(l-piperidnyl)-l,2,4,4a,5,6,7,8,9,10-dec-ahydro derivative formed, which could be converted into the l,2,4,4a,7,8,9,10-octahydro derivative by heating at 150 °C. Cyclization of iV-[(2-butyl-2-oxoethoxy)acetyl]-3,4-dimethoxyphenylethylamine on the action of TFA gave llb-butyl-1,3,4,6,7,1 lb-hexahydro[l,4]oxazino[3,4- ]isoquinolin-4-one <1997JOC2080>. 

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