已经开发出在催化量的偶氮二(异丁腈)作为自由基引发剂的存在下,二炔和硫代乙酸的单步分子内自由基级联反应以合成噻吩。该方法允许容易且有效地构建具有3,4-稠环取代和未取代的2,5-位的噻吩支架,用于进一步的官能化和聚合。使用该方法,合成了环戊[ c ]噻吩,3,4-乙撑二氧噻吩和含噻吩的螺环化合物的衍生物。
Working three shifts: Polyconjugated δ‐diketones are formed stereoselectively in high yields by the gold‐catalyzed rearrangement of 1,6‐diyn‐3‐yl esters. This cascade involves a 1,3‐sigmatropic acyloxy shift, a 5‐exo‐dig cyclization of the resulting allenyne, and an unprecedented 1,5‐sigmatropic shift of an acyl fragment. The usefulness of the products was shown by an efficient acid‐catalyzed transformation
The ruthenium-catalyzed hydrocarbamoylative cyclization of 1,6-diynes with formamides afforded exocyclic-diene-type α,β,γ,δ-unsaturated amides with 100% stereoselectivity. A plausible mechanism involving ruthenium hydride species is proposed to explain the experimental results. Some control experiments, performed using DMF-d7 and/or D2O, corroborate the proposed mechanism.
selection of chiral ligands is examined to gain additional information about the scope of the new asymmetric Huisgen ‘click’ reaction [the desymmetrisation of bis-alkynes usingchiral ligands in conjunction with the widely applied copper-catalysed azide–alkyne cycloaddition (CuAAC) triazole synthesis]. The development of a new chiral assay for (±)-methyl 2-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]-2-cyanopent-4-ynoate
A new furan annelation by the palladium-catalyzed reaction of 2-alkynyl carbonates with β-keto esters is described. The reaction proceeds under mild neutral conditions and hence unstable 3-alkylidene-2,3-dihydrofurans can be prepared in this way. Similarly, reaction of 2-(1-alkynyl)oxiranes with β-keto esters gives alkylidene furans.
Cyclization/Hydrosilylation of Functionalized 1,6-Diynes Catalyzed by Cationic Platinum Complexes Containing Bidentate Nitrogen Ligands
作者:Xiang Wang、Harinath Chakrapani、James W. Madine、Michele A. Keyerleber、Ross A. Widenhoefer
DOI:10.1021/jo015986p
日期:2002.5.1
and HSiEt(3) to form 1,1-dicarbomethoxy-3-methylene-4-(triethylsilylmethylene)cyclopentane (3) in 82% isolated yield with 26:1 Z:E selectivity. Platinum-catalyzed diyne cyclization/hydrosilylation tolerated a range of functional groups including esters, sulfones, acetals, silyl ethers, amides, and hindered ketones. Diynes that possessed propargylic substitution underwent facile cyclization/hydrosilylation