Highly regioselective decarboxylative Claisen rearrangement reactions of diallyl 2-sulfonylmalonates

The decarboxylative Claisen rearrangement of a range of substituted diallyl 2-sulfonylmalonates is described. The substrates are made by C-carboxylation of the corresponding allyl sulfonylacetates with allyl para-nitrophenyl carbonates. The reactions display a high degree of regioselectivity, with allylic substituents possessing electron-rich substituents at the allyl three-position rearranging preferentially.     

Synthesis of 2-iminothiazoline derivatives by sequential conjugate addition/annulation/ring-opening reactions

1,2-Diaza-1,3-butadienes reacted with rhodanine affording 2-(mercaptoacetyl)iminothiazoline derivatives through conjugate addition/annulation/ring-opening/oxidative dimerization. The hypothesized ring-closure and ring-opening mechanism was supported by X-ray crystal structure analysis of a compound obtained by reaction of the same reagents with a chiral 1,3-oxazolidine-2-thione derivative.     

Highly regioselective diels-alder reactions of 2-trimethylsilylmethyl- and 2-trimethylstannylmethyl-1,3-butadiene

2-Trimethylsilylmethyl and 2-trimethylstannylmethyl-1,3-butadiene undergo facile cycloaddition with dienophiles, and show high regioselectivity with unsymmetrical dienophiles.     

Highly regioselective palladium/copper-catalysed cross-coupling reactions of terminal alkynes and allenes

The Pd/Cu-catalysed cross-coupling reaction of heterocyclic terminal alkynes and allene/allenyl heterocycles affords novel trisubstituted en-ynes in good yield.     

Comparison of Ru- and Mo-based chiral olefin metathesis catalysts. Complementarity in asymmetric ring-opening/cross-metathesis reactions of oxa- and azabicycles

A comparative study of chiral Mo- and Ru-based catalysts to promote enantioselective synthesis of 2,6-disubstituted pyrans and piperidines through asymmetric ring-opening/cross-metathesis (AROM/CM) reactions is presented. These studies demonstrate the critical complementarity that exists between the two classes of chiral catalysts.     

Highly regioselective thiocarbonylation of conjugated dienes via palladium-catalyzed three-component coupling reactions

Three-component coupling reaction of conjugated dienes, thiols, and carbon monoxide affords an atom-economical thiocarbonylation of the dienes to give beta,gamma-unsaturated thioesters as the sole products. A catalyst system based on [Pd(OAc)(2)] and Ph(3)P showed excellent catalytic activity. The thiocarbonylation was performed under an atmosphere of carbon monoxide (400 psi) at 110 degrees C in CH(2)Cl(2) for 60 h. A wide variety of thioesters were synthesized in good to excellent yields from easily accessible starting materials. The reaction is believed to proceed via a eta(3)-allylpalladium intermediate. The thiocarbonylation, which is applicable to a wide variety of conjugated dienes, occurs in high regioselectivity, the latter dependent on the steric characteristics and stability of the eta(3)-allylpalladium complex.     

Highly regioselective heterocyclization reactions of 1H-1,2,4-triazole-3-thiols with chloroacetylenephosphonates

1-Chloroacetylene-2-phosphonates react with 1H-1,2,4-triazole-3-thiols in anhydrous acetonitrile with high regioselectivity to form the fused heterocycles, 6-(dialkoxyphosphoryl)-3H-thiazolo[3,2-b][1,2,4]triazol-7-ylium chlorides 1-5. A significant difference from the previously known reactions of binucleophiles with haloacetylenes is the involvement of both acetylenic carbon atoms in the heterocycle formation. A reaction mechanism is hypothesized that assumes the formation of a sulfenium cation at the acetylene C-1 atom followed by attack of the C-2 atom by the ring N-2 atom. Compounds 1-5 easily lose one alkyl group from the dialkoxyphosphoryl fragment to form zwitterions (e.g., 6-8) which further can be transformed into inner salts 9 and 10 when heated with concentrated hydrochloric acid.     

Highly regioselective coupling reactions of allylic and propargylic alcohol derivatives with gamma,gamma-dialkoxyallylic zirconium species via Zr-to-Cu transmetalation

In the presence of CuCN, reaction of gamma,gamma-dialkoxyallylic zirconium species 4, generated in situ by treating triethyl orthoacrylate with zirconocene-butene complex, with allylic and propargylic phosphates proceeded at the alpha-position of 4 in a highly SN2'-selective manner to give the corresponding 5-alkenoates and 4,5-alkadienoates, respectively. In the present Cu(I)-mediated coupling reaction, the gamma,gamma-dialkoxyallylic zirconium species 4 serves as a synthetically useful homoenolate anion equivalent of propionate.     

Highly regioselective catalytic oxidative coupling reactions: synthetic and mechanistic investigations

A highly efficient and regioselective Pd-catalyzed method for the oxidative coupling of arylpyridine derivatives is reported. Remarkably, the reactions proceed at room temperature and are compatible with diverse functionalities, including aryl halides and thiophenes. Mechanistic studies suggest that these transformations proceed via a previously unprecedented mechanism involving two different pyridine-directed C-H activation reactions-one at a PdII center and one at PdIV.     

Microwave-accelerated cross-metathesis reactions of N-allyl amino acid substrates

Microwave heating has been utilised for the cross-metathesis reaction of N-allyl amino acid substrates to generate olefin homodimers. Remarkable acceleration of the cross-metathesis reaction (minutes compared to hours) over conventional reflux heating was observed. In addition, improved reaction yields and similar E/Z ratios for the cross-metathesis products were achieved.     

Tandem cross-metathesis/hydrogenation/cyclization reactions by using compatible catalysts

[reaction: see text] A one-pot tandem cross-metathesis/hydrogenation/cyclization procedure was achieved at room temperature, under 1 atm of hydrogen, in the presence of a ruthenium catalyst and PtO(2) showing the compatibility of the two catalysts. This tandem reaction allows the synthesis of substituted lactones and lactols from acrylic acid and acrolein, respectively, in the presence of unsaturated alcohols.     

Highly regioselective synthesis of 1,3-diiodonaphthalene derivatives via a sequential cascade iodocyclization

A novel and flexible sequentially cascade iodocyclization for the synthesis of highly substituted 1,3-diiodinated naphthalene derivatives in up to 99% yield under mild conditions is reported. The dihalogenated moiety can be readily introduced into the naphthalenes in a position that is usually not easily functionalized.     

A novel method for regioselective ring-opening reduction of 4,6-O-benzylidene hexopyranoside derivatives using CoCl2 and BH3·THF

A novel and facile reductive ring-opening reaction for 4,6-O-benzylidene acetal derivatives of hexopyranosides using CoCl₂/BH₃·THF gave the corresponding 4-O-benzyl-6-OH derivatives selectively in good yields. This convenient method should allow large-scale synthesis at low cost.     

Trisubstituted aziridine ring-opening by phenol derivatives: stereo- and regioselective formation of chiral tertiary alkyl-aryl ethers

An unprecedented stereo- and regioselective trisubstituted aziridine ring-opening by phenol derivatives was discovered. The reaction features very mild reaction conditions and broad functional group compatibility, which provides a good method for the stereoselective formation of tertiary alkyl-aryl ethers in highly functionalized systems. [reaction: see text]     

Highly regioselective anti-markovnikov palladium-borate-catalyzed methoxycarbonylation reactions: unprecedented results for aryl olefins

[Structure: see text] A general, highly efficient and regioselective methoxycarbonylation, by means of a palladium-salicylicborate-catalyzed protocol, of terminal alkyl and aryl olefins is described. The substrates include aliphatic alkenes, allylbenzenes, and styrene derivatives. The yields are very good (60-92%) and the regioselectivity, in favor of the linear ester, is up to quantitative--unprecedented in the case of styrenes.     

Highly regioselective palladium-catalyzed annulation reactions of heteroatom-substituted allenes for synthesis of condensed heterocycles

We have developed a highly regioselective synthesis of heterocycles via palladium-catalyzed annulation reaction of heteroatom-substituted allenes. Various aryl halides were reacted and one regioisomer was observed exclusively in all reactions. In addition, subsequent functionalizations of annulated products were carried out using alkyl metal reagents, and the introduction of alkyl moieties was accomplished.     

银催化羧化偶联反应及钌催化交叉复分解反应串联合成官能团炔酸酯

通过将Ag催化的羧化偶联反应与Ru催化的交叉复分解反应串联, 用端炔、二氧化碳、端烯基取代的溴代物和甲基丙烯酸甲酯高效高产率地合成了一系列官能团化的炔酸酯.