The Hypohalite Reactions

The photolysis of a tertiary hypohalite (readily prepared from the corresponding alcohol) generates alkoxy radical, which abstracts hydrogen from 5-carbon to produce an alkyl radical. The resulting alkyl radical abstracts halogen atom from a second molecule of the hypohalite to give 5-haloalcohol, which is cyclized in presence of a base to form a tetrahydrofuran derivative [9]. These reactions are very similar to the Barton reaction and proceed through a six-membered cyclic transition 

For example, the hypochlorite 11 of 2-methyl-2-hexanol gives tetrahydro-furan derivative 12. 

This method has been used in the synthesis of steroids for introduction of functionality at angular methyl groups. For example, steroid 13 gives 14 [10]. 

In the hypochlorite reactions, intramolecular hydrogen abstraction competes with p-cleavage and other reactions. For example, tertiary hypochlorite 15 on photolysis gives ketones and alkyl chlorides from P-cleavage and radical coupling reactions [10]. 

The hypohalite method of lead tetraacetate and iodine has been applied in the preparation of a key intermediate 18 for the synthesis of labdane diterpene, manool 18a [13]. 

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Diraethyldihydroresorcinol (dimedone) is converted into 3,3-di-methylglutaric acid on treatment with sodium hypochlorite or sodium hy-pobromite. As a p-diketone, it suffers alkaline hydrolysis to 3,3-dimethyl-5-ketohexanoic acid, which undergoes regular hypohalite degradation of the methyl ketone end (equation 429) [735. Both the hydrolytic opening of the ring and the hypohalite reaction are accomplished in one step [699],... 

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