PHOTOCHEMISTRY OF ALKYL NITRITES

Miscellaneoas Reactions.—Little interest has been shown this year in the photochemistry of alkyl nitrites. Irradiation of the acetylenic nitrite (230) 1 to the formation in poor yield of y-butyrolactone (231). A mechanism involving cyclization of the alkoxy-radical, followed by formation of the spiro-intermediate (232), is shown in Scheme 18. The intramolecular addition of thiiyl radical to... 

In contrast to the intramolecular hydrogen abstraction mentioned above, fragmentation, another principal reaction of alkoxyl radicals, was seldom used in organic synthesis until the 1970s. An analysis of the numerous examples reported in the past and our own results concerning the photochemistry of alkyl nitrites and hypohalites indicated that the direction of 3-fragmentation in unsymmetrical substrates is the outcome of an interplay of multiple factors, such as the relative thermodynamic stability of the resultant radicals, ring strain, and stereoelectronic factors. 

Alkyl hypochlorites and hypobromites are relatively stable molecules alkyl hypoiodites can only be prepared in situ, usually by the reaction of alcohols with metal acetates or oxides and iodine or by the reaction of alcohols with a hypervalent iodine compound and iodine.1319 Alkyl hypochlorites and hypoiodites can be utilized in reactions that parallel those of the organic nitrites (Barton reaction Section 6.4.2). For example, the photochemistry of the steroidal hypoiodite 497, prepared by the reaction of the corresponding alcohol with iodine oxide (I2O) generated from mercury(II) oxide and molecular iodine in situ, affords a new five-membered ring via an O I bond fission, 1,5-hydrogen abstraction and substitution (Scheme 6.244).1353... 

Kabasakahen, P., E.R. Townley, and D. Yudis (1962), Photolysis of nitrite esters in solntion. m. Photochemistry of primary, secondary and tertiary alkyl nitrites, J. Am. Chem. Soc., 84, 2718-2722. 

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