A method for the preparation of 5-aryl-2,3-dihydrofuran-4-carboxylates has been developed. Exposure of 4-(arylmethyl)oxy-2-diazobutyrates to 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) effected oxidative generation of oxocarbenium intermediates, which underwent intramolecular attack of the diazo carbon atom and subsequent β-elimination to give 5-aryl-2,3-dihydrofurancarboxylates in modest to good yields. In particular, tertiary arylmethyl ethers offer the advantages of enhanced reactivity toward DDQ and higher product yields due to a Thorpe−Ingold effect. To demonstrate the synthetic utility of the cyclization reaction, selective transformations of an aromatization-prone dihydrofuran product are also described.
- diazo compounds
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