Blanc rule

Blanc rule org chem The rule that glutaric and succinic acids yield cyclic anhydrides on pyrolysis, while adipic and pimelic acids yield cyclic ketones there are certain exceptions. blar k, rul ... 

Blanc reaction-Blanc rule. Cyclization of dicarboxylic acids on heating with acetic anhydride to give either cyclic anhydrides or ketones, depending on the positions of the carboxyl groups 1,4- and 1,5-diacids give anhydrides, while diacids in which the carboxy groups are in 1,6- or further-removed positions give ketones. 

The size of each of the rings present in steroids was established by serial oxidation reactions starting with what would later be dubbed ring A. The empirical, so-called Blanc, rule holds that oxidation of a cyclohexanone (4-1) (Scheme 1.4) proceeds to afford a dicarboxylic acid (4-3), likely through the enol form, 4-2. Heating the diacid 4-3 with acetic anhydride proceeds to cyclopentanone 4-4 with loss of one carboxyl carbon. Repeated oxidation of that intermediate again results in a dicarboxylic acid, in this case adipic acid (4-5). Exposure to hot acetic anhydride leads to anhydride... 

Other references related to the Blanc rule are cited in the literature. 

One study showed that the Cram s rule product predominates with metal hydride reducing agents, but the other product with Bouveault-Blanc and dissolving metal reductions Yamamoto, Y Matsuoka, K. Nemoto, H. J. Am. Chem. Soc. 1988, 110, 4475. 

A cyclic ketone (XLIV), consistent with Blanc s rule, is formed by heating a mixture of l,2-bis(carboxymethyl)carborane (XLIII) and barium carbonate under vacuum 334). 

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