New 4-(trifluoromethyl)tetrahydrothiophenes containing an ester, sulfone, sulfoximine, sulfonamide, or phosphonate moiety at position 3 were synthesized by 1,3-dipolar [3?+?2]-cycloaddition reactions of 3,3,3-trifluoropropene derivatives and thiocarbonyl ylide generated in situ from chloromethyl trimethylsilylmethyl sulfide. 相似文献
Multicomponent reactions of phosphines, enynedioates and cinnamaldimines generated 3‐phosphorus ylide γ‐lactams having a 1,3,5‐hexatriene moiety with low activation energy barrier for 6π electrocyclization, through initial formation of 1,3‐dipoles from the α(δ′)‐Michael addition of phosphines to enynedioates. The reactive 1,3‐dipoles underwent addition to cinnamaldimines, lactamization, 6π electrocyclization and oxidation to give 3‐phosphorus ylide oxindoles as platform molecules toward isatins and isoxazolinones. The key step, 6π electrocyclization, was further examined by a kinetic and a computational study.
Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of strong SH-acids, such as 2-mercapto-1-methylimidazole and 2-thiazoline-2-thiol. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon–carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group. 相似文献
The 1,3-dipolar cycloadditions of C,N-diphenylnitrone, C-phenyl-N-methylnitrone, triphenylnitrone, mesitylnitrile oxide and tetracyanocarbonyl ylide with 1,1-difluoroallene (DFA) are reported and discussed with respect to regiochemistry. Each of the dipoles adds exclusively to the C2—C3, non-fluorine-substituted π-bond of DFA. The nitrones all undergo regiospecific reactions while mesitylnitrile oxide does not. The results are discussed with respect to FMO theory and other factors which can give rise to regiochemical variation. 相似文献
A new efficient method for the stereoselective preparation of trans‐2,5‐bis(alkyloxymethyl)pyrrolidines ( 7 ) using easily available starting materials is described. The main step of this synthesis is the stereoselective formation of the pyrrolidine ring by the 1,3‐dipolar cycloaddition reaction of an in situ generated azomethine ylide. Both enantiomers of the C2‐symmetric auxiliaries are prepared separately in a short reaction sequence. 相似文献
Solution terpolymerization of styrene (Sty), acrylonitrile (AN) and copper acrylate (CuA) has been carried out in dimethylformamide at 90°C for 4 h using p-acetyl benzylidene triphenylarsonium ylide as radical initiator. 1H nuclear magnetic resonance (NMR), IR and elemental analysis have been used to characterized the terpolymer. Analysis of kinetic data indicates the following rate equation: The overall activation energy is 38 kJ mol−1. The composition of terpolymer calculated from NMR and elemental analysis has been used to evaluate reactivity ratios as r1(Sty) = 5 ± 2 and r2(AN + CuA) = 0.4 ± 0.02 employing the Finemann–Ross method, which confirms its random origin. The terpolymer was thermally stable up to 2007deg;C. 相似文献
Differently substituted hetaryl thioketones react with less reactive diazoketones under microwave (MW) irradiation in toluene solution. After only 2?min, the reactions were complete and, depending on the type of the used diazoketone, α,β-unsaturated ketones, acyl substituted thiiranes or 1,3-oxathioles were obtained as final products. In the case of azibenzil and di(thiophen-2-yl) thioketone, a new type of 1,5-dipolar electrocyclization of the intermediate thiocarbonyl ylide involving a thiophene ring led to a fused sulfur heterocycle. In contrast to hetaryl thioketones, the ferrocenyl analogues decompose under MW irradiation. Alternatively, they react with diazopropanone and 2-diazo-1-phenylethanone in boiling THF in the presence of LiClO4 to give α,β-unsaturated ketones as sole products. In these cases, the reactions require long reaction times. 相似文献