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The chemo- and stereoselective one-pot synthesis of functionalized trifluoromethylated 4,5-dihydrofurans was developed. It consists in the treatment of fluorinated 2-haloenones with 1,3-dicarbonyl compounds (1,3-diketones and β-keto esters). The reaction was generally found to proceed in moderate to good yield and excellent selectivity. The mechanism of the assembly of these heterocycles is discussed in terms of multi-step processes involving formation of Michael adduct followed by cyclization through the classical intramolecular halogen nucleophilic substitution at sp3 carbon atom.

Lithiated allenes or allenylmagnesium bromides readily react (THF/hexane, m 90 to m 105°C, 10-15 r min) with phenylsulfinylamine to give N -phenyl-2-alkynylsulfinamides. The reaction z of metallated 3-methylbuta-1,2-diene leads to the formation of not only 2-methyl- N -phenylbut-3-yne-2-sulfinamide, but also its allenic isomer, 3-methyl- N -phenylbuta-1,2-diene-1-sulfinamide. Metallated penta-1,2-diene, 1-propa-1,2-dienylcyclohexane and 4,4-dimethylpenta-1,2-diene react with phenylsulfinylamine to form acetylenes 3 , 4 and 6 respectively as a mixture of diastereoisomers.

A number of N-(5,5-dimethyl-2(5H)-thiophenyliden)amines and N-(1-thiaspiro(4.5)dec-3-en-2- yliden)amines, existing exclusively in one isomeric form, have been obtained in good to excellent yields by reaction of lithiated 1,1-disubstituted 1,2-dienes with isothiocyanates followed by treatment with t-BuOH and t-BuOK in DMSO. Investigation of the isomeric structures using 1H, 13C, 15N, 2D NOESY NMR spectroscopy and quantum-chemical calculation (ab initio HF/6-31G*) of the total energies of the fully optimized geometries indicated that for both N-(5,5-dimethyl-2(5H)-thiophenyliden)methanamine and N-(1- thiaspiro(4.5)dec-3-en-2-yliden)methanamine the Z-isomers are more stable, the energy differences with respect to E-isomers being 3.37-3.87 kcal/mol. It was established that the chair conformer with axial orientation of sulfur of (Z)-N-(1-thiaspiro(4.5)dec-3-en-2- yliden)methanamine the has the lowest energy of all possible conformers.

1H and 13C chemical shifts and 1H,1H, 13C,1H and 13C,13C coupling constants were determined for a series of O-vinyl ketoximes. The analysis suggests that O-vinyl ketoximes are conformationally homogeneous. These exist as a mixture of s-trans/s-trans and s-trans/s-cis conformers, the former being energetically preferable. The proximity effects for 1H and 13C NMR parameters allow one to detect the stereo-orientation of asymmetric substituent relatively to the ketoxime moiety. Copyright © 2000 John Wiley & Sons, Ltd.

Being polydentate nucleophiles, capto-dative enaminones are regiospecifically protonated at the N or β-C atom depending on the nature of the protonating reagent.

Being polydentate nucleophiles, capto-dative enaminones are regiospecifically protonated at the N or β-C atom depending on the nature of the protonating reagent.