Ketodecarboxylation of carboxylic diacids

The retentive power of graphite towards adipic acid and the catalytic effect of the magnetite, especially present in A, are obvious. TEM examination of a graphite A before and after reaction showed that crystallites of Fe304 seemed to be smaller 

Some MW-promoted decarboxylations have been reported in the literature [92], even the decarboxylation of magnesium, caldum and barium salts of alkanoic 

Entry Graphite and added catalyst MW conditionsl l Yield (%)W1 

Graphite A was again superior, giving, under these optimized conditions (entry 2), a 90% yield in cydopentanone (84) after only 6x2 min irradiation. Under the same conditions, graphite B gave only a 33% yield (entry 4). 

Because Fc304 itself strongly absorbs MW [4] and is good catalyst for decarboxylations [91], is the graphite necessary When Fc304 was used in the absence of graphite, the yield of ketone 84 decreased dramatically (10%) (Table 9.9, entry 13). 

The catalytic cyclization of a diacid requires two contradictory thermal conditions a temperature high enough to have a convenient reaction rate, but low enough to 

3 Mass of 70 2.19 g (15 mmol) mass of graphite 5 g b Sequential MW irradiation controlled to a maximum temperature of 450 °C c Applied incident power and irradiation time interval between two irradiations 2 min d Yield of cyclopentanone (74) from GC analysis 

To compare their activities further, various catalysts were added to graphite B, and the results were analyzed with respect to the reference experiment (Tab. 7.10, entry 3) which gave a low yield (19%). When doped with Fe304, graphite B gave a 51% conversion of 70 (entry 5), almost as much as graphite A alone (entry 1). The two 

Comparison of reaction times revealed a shortening under MW irradiation (Tab. 7.10, entry 2 overall reaction time = 22 min) with respect to conventional heating (Tab. 7.9, entry 1, 30 min), for the same maximum temperature. This can be explained by a higher temperature gradient and the presence of hot spots at the graphite surface under MW. 

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Use of graphite-supported methodology has been reported for three types of reaction - the Friedel-Crafts acylation [15, 16, 27, 66], the acylative cleavage of ethers [15, 16], and the ketodecarboxylation of carboxylic diacids [67, 68], either with conventional heating (GS/A) or MW irradiation (GS/MW coupling) these are discussed below. First, however, we describe the analysis of two commercial graphites of different purity which are used for these experiments. 

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