Reaction of ethoxycarbonylcarbene with n-hexadecane and n-docosane

Abstract

The reaction of both thermally and photolytically generated ethoxycarbonylcarbene with high molecular weight n-alkanes (> C₁₀) gives the expected C–H bond insertion products, e.g., ethyl esters of isomeric C₁₈ acids in the case of n-hexadecane. The thermally generated species gave much higher yields, up to 75% based on the carbene precursor, ethyl diazoacetate; possible explanations are discussed. A novel variation in reactivity of the carbene towards the secondary positions of an n-alkane has been observed. In the photolyses, the relative rate of insertion of ethoxycarbonylcarbene for secondary C–H:primary C–H was found to be 2·1 at position 2, steadily falling to ca. 1·4 at the secondary positions in the middle of the chain. Similar trends were noted in thermal reactions. Other products of the reactions are described.