Hydroxyalkylation with α-Hydroperoxydiazenes. Alcohols from Olefins and Carbonyl Compounds from Enol Ethers

Article abstract of DOI:10.1021/jo00176a023

Alkyl(1-hydroxy-1-methylethyl)diazenes 2a-f <(CH3)2C(OOH)N=NR: a,R=CH2CF3;b,R=CH2CH2CN;c,R=CH2CH(CH3)CN;d,R=CH2CH2OCH3;e,R=CH2CH2OC6H5;f,R=CH2CH2CH2OC6H5)> were prepared in solution by autoxidation of the corresponding hydrazones of acetone.Thermolysis of the diazenes at 50-80 deg C in alkenes leads to alcohols.For example, 2b decomposes in 1,1-diphenylethene to afford 5-hydroxy-5,5-diphenylpentanenitrile.Alkenes with abstractable allylic hydrogens gave analogous products, but in very low yield.Thermolysis of a diazene 2 in an enol ether solvent leads to an aldehyde or a ketone.Thus, 2a decomposes in 1-ethoxyethene and in 2-methoxypropene to afford, respectively, 4,4,4-trifluorobutanal and 5,5,5-trifluoro-2-pentanone.Yields lie in range from 50percent to 70percent.The thermolysis of 2 in alkenes involves radical intermediates and radical chain hydroxyalkylation of alkene double bonds.In one chain-propagating step, R*, generated from 2, adds to the alkene.The adduct radical so formed propagates by inducing decomposition of 2 by attack at hydroxyl oxygen.According to this mechanism, initial products from enol ethers are hemiacetals or hemiketals which do not survive the reaction conditions but decompose to the corresponding carbonyl compounds.Preliminary evidence for this mechanism is presented.