Thermal decarboxylation 494 Subject

Blood Thermally decarboxylated subjected to static headspace analysis GC/ECD (for metabolite trichloroacetic acid) 2 ppb 101-109 Ziglio et al. 1984... 

A total synthesis of (+)-55 was performed by Cushman et al. 69) (Scheme 17). It was based on cycloaddition of Schiff base 68 to anhydride 69. The addition product 70, received in the form of a mixture of diaste-reomers, was then subjected to thermal decarboxylation to give rise to diastereomer 71 with the desired trans configuration as the major product. The latter upon methanolysis and selective reduction furnished (+)-55. 

Not only thermal [2 + 2] cycloaddition reactions but also the corresponding [2 + 2] cycloreversions are subject to large solvent effects. A good example is the thermal decarboxylation of the y9-lactone trani -3- -butyl-4-phenyloxetan-2-one, as described in Eq. (5-36). 

Show the outcomes of subjecting the Michael reaction products in Problems 15.36a and 15.36b to hydrolysis, followed by acidification, followed by thermal decarboxylation. (See Example 15.11)... 

The dibromofuran 2.40 was subjected to a sequence of Stille coupling reactions, the second one requiring a more robust catalyst, leading to rosefuran 2.43 after hydrolysis and copper-catalysed thermal decarboxylation (Scheme 2.15). A quite different synthesis of rosefuran may be found in Scheme 11.48. 

Thermally labile [FeCp(C0)2(C(0)0H)] is subject to decarboxylation, while [FeCp(C0)(PPh3)(C02)K] is isolated by treatment of [FeCp... 

A second and may be more important point is their low thermal stability which may open a new way for decarboxylative fluorination of various acids - a subject which we have started to explore not a long ago (figure 8). 

By far, the most often used nucleophiles are malonates, which can be deproto-nated by the aUcoxide formed in the reaction of allyl carbonates or by an added base such as NaH. This standard nucleophile has been applied in all types of aUylations, and many applications are also reported in this monograph. The nucleophihc species can also be generated by 1,4-addition, for example, of alkoxides, generated from carbonates, onto alkylidenemalonates both inter- and intramolecularly [92]. The substitution products can be subjected to a thermal desalkoxycarboxylation or, after hydrolysis, decarboxylation, giving rise to carboxylic esters or acids [93]. Therefore, in combination with this decomposition, malonates can also be used as surrogates for ester enolates [94], which generally cannot be used as nucleophiles in allylations. 

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