Pyrolysis of chloroformates

Flash vapor pyrolysis of chloroform has been used to effect the... 

Wentrup and co-workers investigated the flash vacuum pyrolysis of isopropylidene (l-methyIpyrrolidin-2-ylidene)malonate (1261) (86CC369) (Scheme 51). When the pyrolysis was carried out at 450°C (10-4 torr, contact time 10 3 sec), and the product was condensed on a cold finger at -196°C, (pyrrolidinylidene)malonic anhydride (1262) could be identified. Malonic anhydride (1262) in chloroform solution at -20°C lost carbon dioxide to give methyleneketene (1263), which was reacted with a few drops of water or methanol to yield acrylates (1264). Flash vacuum pyrolysis of 1261 at higher temperature (800°C) gave pyrrolopyrrolone (1265). The products were characterized by IR and 13C-NMR data. 

Primary Conversions and Influence of Mobile Phase Yields for the various H-donor and non-donor solvent extractions of Linby coal at 400% are summarised in Table III the conversions for the THF-extracted coal include the extracted material. Surprisingly, pre-extraction with THF significantly increases primary conversions in the polynuclear aromatic compounds (PACs) investigated. These findings appear to be contrary to those of other liquefaction (16) and pyrolysis (17) studies where prior removal of chloroform-extractable material significantly reduced conversions. However, Rincon and Cruz (18) have reported recently that pre-swelling coals in THF increases conversions for both anthracene oil and tetralin. The fact that Point of Ayr (87% dmmf C) coal yielded over 80% pyridine-solubles in pyrene (C.E. Snape, unpublished data) without pre-extraction is consistent with the earlier results of Qarke et al (19) for anthracene oil extraction where UK coals... 

Vapor phase pyrolysis of 2-aminobiphenyl in chloroform at 350°C produces carbazole,as does heating at 500-800°C in a high-frequency glow discharge at 25-34 A small amount (11%) of carbazole 280 was formed during the reaction of 281 with copper-potassium carbonate and 1-iodo-naphthalene in nitrobenzene. ... 

The eastern Oklahoma coals were obtained from the Oklahoma Geological Survey Organic Petrography Laboratory where they had been crushed to -20 mesh and analysed on an as received basis (Table I). The whole, crushed coals were extracted for 48 hours with a 1 1 (v/v) mixture of chloroform/methanol using a soxhlet apparatus. Exhaustive extraction ensures that soluble compounds are removed and that the compounds produced during pyrolysis are derived from the organic matrix of the coal. 

Pyrrolo 2,3-/ Ipyridine (75) underwent pyrolysis in chloroform to give a separable mixture of 1,8-naphthyridine (76, R=H) and 3-chloro-l,8-naphthyridine (76, R=C1) (vapor phase, 550°C low yields).1145... 

The use of selectivity data as a means of identifying intermediates has been employed effectively. For example, in the dichlorocyclo-propanation of olefins, the selectivity of attack using CC12 generated by different methods (the pyrolysis and a elimination of chloroform) was found to be almost identical (Skell and Cholod, 1969a). This was... 

Addition of aryl tellurium trihalides to cyclohexene produces trails-] -aryldihalotelluro-2-halocyclohexanes when the reactions are carried out in chloroform, and trans-1-aryldihalotelluro-2-methoxycyclohexanes when methanol is used as the reaction medium. Treatment of the 2-chlorocyclohexyl 4-methoxyphenyl tellurium dichloride with terf.-butyl hydroperoxide in acetic acid yielded tram-l,2-dichlorocyclohexane and aryl chloride. Bis[4-methoxyphenyl] tellurium dichloride did not yield any aryl chloride under these conditions1. Pyrolysis of tran.s-2-methoxycydohexyl phenyl tellurium dibromidc afforded Crum- l-bromo-2-methoxycyclohexane1. 

Pyrolysis of CHs-labeled 1-methylpyrazole 853 with chloroform at 550 °C in a continuous flow reactor yielded unlabeled 2-chloropyrimidine 854 and 2-cyanopyrrole 855 labeled at the cyano groups (Equation 189) <1997J(P1)3581>. However, pyrolysis of 1-benzyIpyrazole with chloroform under similar conditions gave 2-chloropyrimidine 854, 2-phenylpyrimidine, and, as the major product, a-carboline. 

The thermal decomposition of chloroform has been studied by a number of workers > > - > > - , the main pyrolysis products near 500 °C being hydrogen chloride, tetrachloroethene and carbon tetrachloride. Semeluk and Bernstein have proposed the following rate equation for the decomposition... 

The thermal decomposition of chloroformates has been further studied (refs. 834, 842, 865, 995) Lennon and Stimson have reported on the pyrolysis of trimethyl acetyl chloride and bromide Dakubu and Maccoll have investigated the elimination of hydrogen chloride from gaseous monochloroketones, and Frey et have reported on the thermal decomposition of 3-chloro-3-methyldiazi-rine. 

The pyrolysis of bismuth dithiocarbomates has commercial potential for the production of Bi2S3 films, which are useful for photodiode arrays or photovoltaics. Normura and coworkers developed techniques for solution pyrolysis and its application to the formation of thin films. They investigated four bismuth dithiocarbomates (Table 5) for the production of films of BijSs . To obtain useful films a solution of the dithiocarbamate in p-xylene or chloroform is heated on a glass substrate at 100 °C for 1 h, cooled to room temperature and finally heated at 250-350 °C... 

Much of the early work described in the literature was centered around vinyl chloroformate classically made by the gas phase pyrolysis of ethylene glycol bis-chloroforma-te at 460-480°C (Ref. Ill, 112,113). However, this route proved to be industrially and economically impracticable because of low yields (11-44%) and formation of large amount of chlorinated side products and tars. Scheme 87 presents the decomposition pathways of ethylene glycol bis-chloroformate. 

Besides the severe difficulties encountered in the scaling up, this process was stymied by the impossibility of generalization to other 1-alkenyl chloroformates. For example in the same conditions, pyrolysis of the bischloro-formate of propylene glycol affords selectively the 1-pro-penyl chloroformate instead of the desired isopropenyl chloroformate as shown in scheme 88 (Ref. 111). 

The quantity of chloroethene generated in this reaction was considered too high to be accounted for solely on the basis of the catalysed pyrolysis of the 1,2-dichloroethane, and the mechanism of the formation of the products can be explained on the basis of the charcoal-catalysed decomposition of the common intermediate chloroformate ... 

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