2H-Pyran-5-carboxaldehydes

SYNS ACROLEIN DIMER, stabiUzed (DOT) 3,4-DIHYDRO-2H-PYRAN-2-CARBOXALDEHYDE 2,3-DIHYDRO-L4-PYRAN-2-KARBOXALDEHYD 2-FORMYL-3,4-DIHYDRO-2H-PYRAN 5-HEXENAL, 2,6-EPOXY- a PYTIAN ALDEHYDE... 

Namely, the reaction of 2-thioxothiazolidin-4-one N-hexanoic acid (116) with 2,5-dimethyl-l-phenylpyrrol-3-carboxaldehyde (117) in methanol under the catalytic action of ethylenediamine diacetate (EDDA) yields 5-[(2,5-dimethyl-l-phenylpyrrol-3-yl)methylidene]-2-thioxothiazolidin-4-one N-hexanoic acid (118) in 79% yield. The hydroxamate derivative of 118 is prepared by reacting this compound with 0-(tetrahydro-2H-pyran-2-yl)hydroxylamine followed by treatment with p-toluenesulfonic acid in methanol to afford compound 121 in 60% yield. Esterification of compound 118 is carried out by using methyl iodide in acetonitrile in the presence of sodium carbonate to give compound 120. The 5-(cyclohexyl)methylidene analogue (119) is obtained in 42% yield by direct reaction of compound 116 with cyclohexanecar-boxaldehyde in methanol under the catalytic action of EDDA. 

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