Oxidation, basic conditions lead tetraacetate

Methods such as the pyrolysis of (106), that do not require strongly basic conditions, have been used to generate arynes in bulk for preparative purposes, and another, even better, method is oxidation of l-aminobenzotriazole (107) with lead tetraacetate ... 

The formation of benzimidazoles by cyclization of aryl amidines can be accomplished in a number of ways, but is usually carried out under anhydrous conditions in the presence of a base. Thus cyclizations of (45 R = OH) induced by benzenesulfonyl chloride in pyridine or triethylamine generally give yields of greater than 60%. The more direct process of oxidizing the parent compounds (45 R = H) with sodium hypochlorite under basic conditions gives even higher yields (70-98%). Intermediates in these reactions are the )V-haloamidines (45 R = C1) a nitrene intermediate may be involved or merely dehydrochlorination with concomitant cyclization (Scheme 25). Alternative cyclization procedures include oxidation of the parent amidines (45 R = H) by manganese dioxide or lead tetraacetate and thermal... 

A version of this type of oxidation, which used a combination of lead tetraacetate and boron trifluoride etherate, allowed the transformation of enamines of cyclic ketones into esters of the corresponding contracted ring, as in the classical Favorskii rearrangement of a-haloketones under basic conditions (Scheme 51). 

---