Nitrenes with furans

The pyranofurooxazoline 109 can be prepared by a nitrene insertion reaction of the corresponding furan 110 upon treatment with ethyl azidoformate at — 50 °C under photolysis conditions. Compound 109 is moisture sensitive, and upon treatment with wet acidic THF was converted quantitatively to the more polar furanopyran 111. The structure and stereochemistry of 109 were proved unambiguously by X-ray diffraction, showing that the nitrene inserted anti to the bridgehead methyl group <1999JOC736> (Scheme 30). 

The nitrenes generated by reduction of 2-(2-nitrophenyl)furan with triethyl phosphite or by thermolysis of 2-(2-azidophenyl)furan in 1,2-dichlorobenzene undergo insertion into... 

Apart from hydrodesulphurization, reactions causing transformation or destruction of the thiophen ring are rather rare. Three interesting examples have been reported. In the first, photolysis of 3-cyanothiophen (22) in furan affords the adduct (23) as the major product. 2-Cyanothiophen behaves in a similar way, and an analysis of permutation patterns has indicated that there is a mechanism involving first the 2,5-bridged compound (24) followed by a walk of the sulphur atom. Anils (25) are converted into pyrroles (26) by triethyl phosphite a similar ring-opening by intramolecular insertion of nitrene has also been shown to occur with o-nitrophenyl-di-(2-thienyl)methanes. ... 

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