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The reaction of tert butyl isocyanide with dialkyl acetylenedicarboxylate affords a highly reactive 1 : 1 intermediate which can be trapped by 1,1,1 trifluoropentane 2,4 dione.

2005 Pyran derivatives R 0340Chemoselective Synthesis of Dialkyl 2-(tert-Butylamino)-6-methyl--5-trifluoroacetyl-4H-pyran-3,4-dicarboxylates. -A direct, efficient and operationally simple approach to the chemoselective synthesis of polyfunctionalized 4H-pyrans (IV) via multicomponent reaction of β-diketone (I) with tert-butyl isocyanide (II) and acetylenedicarboxylates (III) is reported. -(ASGHARI*, S.; ZATY, M.; SAFIRI, S.; Russ.

Cyclobutenes are important intermediates in organic synthesis, 1,2 and their synthesis continues to attract much attention. Although the common 5-, 6-and 7-membered ring cycloalkenes are produced fairly easily by intramolecular Wittig reaction, the formation of cyclopropenes and cyclobutenes has not received much attention. 3,4 We have recently described synthesis of cyclobutene derivatives from the stereoselective intramolecular Wittig reaction of a vinyltriphenylphosphonium salt with acetoacetanilide in boiling benzene. 5 Cyclobutenes 1 undergo electrocyclic ringopening reaction in boiling toluene to produce highly electron-deficient 1,3-dienes 2.

A Facile Stereoselective Synthesis of Functionalized Cyclobutenes and Electron--Deficient 1,3-Dienes. -Reaction of ethyl 4,4,4-trifluoroacetoacetate (I) with dialkyl acetylenedicarboxylate (II) leads stereoselectively to the cyclobutenes (III) via an intramolecular Wittig reaction. Compounds (III) are converted into electron-deficient 1,3-dienes (IV) on the basis of conrotatory opening. -(ASGHARI*, S.; ZATY, M.; BIJANZADEH, H. R.; J.