Heusler-Kalvoda reaction

A particularly nice conversion is the reaction of a cyanohydrin with h and Pb(OAc)4 (the Heusler-Kalvoda reaction Scheme 3). ° After the abstraction of a 8-hydrogen the cyano group migrates to the resulting radical. The final product has a ketone in place of the original cyanohydrin, which was of course form from that ketone, and a cyano group on the carbon 7 to the ketone. 

A functionalization that converts C—H bonds to C— NO bonds occurs when nitrite esters are photo-lyzed (the Barton reaction Scheme 4). Again an alkoxyl radical abstracts a 8-hydrogen, and the resulting carbon radical picks up NO. The product nitroso compounds convert easily to oximes. Particularly valuable examples have bMn studied in the steroid field. If the photolysis is performed in the presence of copperfll) acetate the intermediate carbon radical can be oxidized to an alkene, rather than capture NO. If the alcohol whose nitrite ester is photolyzed is part of a cyanohydrin, then the Heusler-Kalvoda reaction occurs, and the product is a ketone with a migrated cyano group (Scheme 5) ... 

For effecting oxidative cyclizations of the types noted, superior results have been obtained with use of the combination lead tetraacetate-iodine, a method introduced by the Ciba-Basel group Ch. Meystre, Heusler, Kalvoda, P. Wieland, Anner, and Wettstein. Known as the hypoiodite reaction because the combination generates HOI, the method appears to be simpler and more efficient than lead tetraacetate alone, and than any of three other methods not employing lead tetraacetate. An improved procedure is as follows. Pregnenolone acetate (5) is first reduced with lithium tri-f-butoxyaluminum hydride in tetrahydrofurane to 3 8-acetoxy-20 -hydroxy-A -pregnene (6) the 20a-isomer is formed in minor amount. At the end... 

General aspects of these reactions are discussed by K. Heusler and J. Kalvoda. ... 

General aspects of these reactions are discussed by K. Heusler and J. Kalvoda.61 Recently the first exception was reported (cf. P. Morand and M. Kaufmann, J. Org. Chem., 34, 2175,1969. 

Heusler, K. and Kalvoda, J., Intramolecular free-radical reactions, Angew, Chem. Int. Ed. Engl., 3, 525, 1964. 

For reviews, see (a) Anbar, M. and Ginsburg, D., Organic hypohalites, Chem. Rev., 54, 925,1954 (b) Heusler, K., and Kalvoda, J., Selective functionalisation of the angular methyl group and further transformation to 19-norsteroids, in Organic Reactions in Steroid Chemistry, Fried, J. and Edwards, J.A., Eds., van Nostrand Reinhold, New York, 1972, chap. 12. 

---