Pyrolysis allenic esters

The photolysis of the furan derivatives 78 yielded the butadienals 79 as the main products [123], Further isomerizations leading to allenic esters used the radiation of a cyclopropene-1 -carboxylic acid ester [124] or applied flash vacuum pyrolysis to 3 -ethoxy cyclobut- 2-en-l-one[125]. 

Since 3-methylenecyclobutane-l,2-dicarboxylic anhydride is easily converted to 3-methyl-2-cydobutene-l,2-dicarboxylic acid, it is an intermediate to a variety of cyclobutenes. The dimethyl ester of 3-methylenecyclobutane-l,2-dicarboxylic acid is also a versatile compound on pyrolysis it gives the substituted allene, methyl butadienoate, and on treatment with amines it gives a cyclobutene, dimethyl 3-methyl-2-cyclobutene-l,2-di-carboxylate. ... 

Another method to prepare allenyl ketones uses flash vacuum pyrolysis of the heterocycles 121 (Scheme 7.19) [163], This elimination of carbon monoxide is at least formally a cheletropic reaction. Highly reactive allenes such as esters and nitriles of type 124 or unsubstituted butadienal can be generated if retro-Diels-Alder reaction of 123 or similar precursors, respectively, is performed by flash vacuum pyrolysis [164]. 

The total contents of saponifiable and free acids in small biological samples were determined by MacGee and Allen [137]. A sample of tissue (3—5 mg) or serum (5—100 /xl) was hydrolysed with a lye, acidified and extracted with /7-hexane. Free acids were extracted from the /7-hexane into a small volume (5—10 ql) of trimethyl-(a,a,a-trifluoro-/ 7-tolyl)ammonium hydroxide. The quaternary salt was injected together with methyl propionate, and methyl esters produced by the pyrolysis were subjected to GC analysis (injection port temperature 240°C, column temperature 180°C, 10% EGSS-X). Comparison of this method with other esterification methods in Table 5.9 shows that it offers at least equally good results. 

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