C-13 NMR CHEMICAL-SHIFTS OF HETEROCYCLES .3. EMPIRICAL SUBSTITUENT EFFECTS IN 2-HALOMETHYL-2-HYDROXY-TETRAHYDROFURANS AND 2-HALOMETHYL-5,6-TETRAHYDRO-4H-PYRANS

Evaluation by empirically derived equations for the substituent effect (alpha, beta, gamma, delta) on the C-13 NMR chemical shifts for C-2, C-3, C-4, C-5, C-6, the halomethyl-substituted carbon (C-7) and the cy ano or oxymic carbon (C-8) in 2-halomethyl-2-hydroxy-tetrahydrofurans 1a-c, 2, 3a, b, 4a and -5,6-tetrahydro-4H-pyrans 5a-c, 6a [with C-2-su bstituents (R(2)): CCl3, CCl3 or CHCl2, C-3-substituents (R(3)): CN, C (Me)=NOH, CH=NOMe, C(Me)=NOMe or CH=NOH], taking as reference the 2-tr ifluoromethyl-2-hydroxy-tetrahydrofuran (1a), is reported. From the ad ditivity properties of the alpha-, beta-, gamma-, delta- and epsilon-e ffects for each substituent it is possible to predict the chemical shi ft of each carbon of the compounds 1-6.