58622-56-3Relevant articles and documents
Catalytic Hunsdiecker reaction and one-pot catalytic Hunsdiecker-Heck strategy: Synthesis of α,β-unsaturated aromatic halides, α- (dihalomethyl)benzenemethanols, 5-aryl-2,4-pentadienoic acids, dienoates and dienamides
Naskar, Dinabandhu,Roy, Sujit
, p. 1369 - 1377 (2007/10/03)
The reaction of α,β-unsaturated aromatic (or heteroaromatic) carboxylic acids with N-halosuccinimides (1 equiv.) and catalytic tetrabutylammonium trifluoroacetate (0.2 equiv.) in dichloroethane results in facile halodecarboxylation affording the corresponding (E)-halides in good to excellent yields. A similar reaction, but with 2 equiv. of N-halosuccinimides in acetonitrile-water (1:1 v/v) results in the exclusive formation of the corresponding α-(dihalomethyl)benzenemethanols. Furthermore, a one-pot strategy has been developed combining catalytic Hunsdiecker reaction (using tetrabutylammonium trifluoroacetate in dichloroethane) and Heck coupling (using palladium acetate/triethylamine/triphenylantimony/dichloroethane) for the synthesis of 5-aryl-2,4-pentadienoic acids, esters and amides in moderate to good yields. The natural product piperine and pipergualamine has been synthesized via the above route. Mechanistic and theoretical studies (via AM1 calculations) provide a useful insight into the mechanism of the present halodecarboxylation reaction, suggesting an ionic pathway involving the attack of the halogenium ion across the carbon-carbon double bond, triggering the elimination of carbon dioxide. (C) 2000 Elsevier Science Ltd.
Oxyanionic Substituent Effect on the C-H Insertion of Carbenes. Reaction of Alkoxides with Dichlorocarbene and Chlorophenylcarbene
Harada, Toshiro,Akiba, Eiji,Oku, Akira
, p. 2771 - 2776 (2007/10/02)
The lithium alkoxides of benzylic, allylic, and simple alkyl alcohols were allowed to react with chloroform in the presence of t-BuOLi in THF-hexane to give, in 32-91percent yields, dichloromethylcarbinols, which were produced by the insertion of dichlorocarbene into the α C-H bond of alkoxides but not by the Wittig rearrangement of carbanions of alkyl dichloromethyl ethers.The enhanced reactivity toward dichlorocarbene of the α C-H bond of alkoxides was clearly demonstrated by the high selectivity of the insertion.The potassium alkoxides of a series of analogous alcohols reacted analogously with benzal chloride in the presence of t-BuOK in THF to give the corresponding substituted oxiranes (16-79percent); e.g., the reaction of potassium benzyl oxide gave 2,3-diphenyloxirane (79percent) as a mixture of stereoisomers (trans:cis = 1.0).With 2-phenethoxide, n-octyl oxide, or 2-methoxyethoxide, the corresponding dialkyl acetals of benzaldehyde were also formed in 9, 6, and 6percent yield, respectively, and their formation is explained in terms of nucleophilic attack of alkoxide on chlorophenylcarbene.With trans-crotyl oxide or 2-phenetoxide, 1,3-diphenylpropan-1-one(33percent) and 1-phenylpent-3-en-1-one (6percent) were produced, respectively, as byproducts through the isomerization of the primary product oxiranes.Oxiranes were produced by the insertion of chlorophenylcarbene into the α C-H bond of alkoxides followed by the cyclization of the intermediate 1-substituted 2-chloro-2-phenethyl alkoxide.These reactions provide us with new preparative methods of synthetically useful dichloromethyl carbinols and oxiranes.
Molecular Rearrangements. 13. Kinetics and Mechanism of Rearrangements of Some Ring-Substituted α-Chlorostyrene Oxides and trans-β-Chlorostyrene Oxides.
McDonald, Richard N.,Cousins, Raymond C.
, p. 2976 - 2984 (2007/10/02)
The synthesis of certain phenyl-substituted derivatives of the isomeric trans-β-chlorostyrene oxides (6) and α-chlorostyrene oxides (7) are reported.The kinetics of rearrangement of 6 (X = p-CH3, H, p-Br, m-Cl, p-NO2) to phenylchloroacetaldehydes (12) in CCl4 buffered by Na2HPO4 and 7 (X = p-CH3, H, p-NO2) to ω-chloroacetophenones in CCl4 were determined by following the rates of disappearance of the α-chloro epoxide and formation of the α-chloro carbonyl product.These substituent effects at 130 deg C were correlated with ?+ constants, yielding ρ values of-3.5 and -0.57 for the rearrangements of 6 and 7, respectively.In nitrobenzene solvent, the kC6H5NO2/kCCl4 for 6 was 180 and for 7 was 1740, the latter solvent effect attributed to nucleophilic solvent participation.It was concluded that these thermal rearrangements of 6 and 7 occur by disrotatory Cβ-O bond heterolysis to yield the corresponding α-keto carbonium-chloride ion pairs.
