On the nucleophilic reactions of 5-trifluoroacetyl-3,4-dihydro-2H-pyran

5-Trifluoroacetyl-3,4-dihydro-2H-pyran react readily with many nucleophiles such as amines and Grignard reagents to give the rign opened products NuCH =(CRR2)-R-1 (R-1: (CH2)(3)OH, R-2: CF3CO). The compound with Nu=Et2N is uns table; it rearranges to 1-hydroxyl-1-trifluoromethyl-2-diethylaminomethylen e-tetrahydropyran and 2-diethylamino-3-trifluoroacetyl-tetrahydropyran via an intramolecular nucleophilic addition reaction. Hydrazine and hydroxylami ne attack the carbonyl carbon of the title compound to form (CH2)(3)OCH=CC( CF3)=NZ(Z = NH2, OH). In the presence of KOH, however, hydroxylamine hydroc hloride reacts additionally to 2-hydroxyl-2-trifluoromethyl-3-cyano-tetrahy dropyran. Upon heating with triethylphosphite, the: title compound reacts a s a heterodiene and gives the corresponding cyclophosphorane. X-Ray diffrac tion analyses of two compound are presented.