本文描述了一种新型的钌催化串联闭环复分解(RCM)双键异构化反应。证明了该方法对五元,六元和七元环状烯醇醚的有效合成的效用。它依赖于易位活性钌卡宾物质到原位异构化活性钌氢化物物质的转化。通过使用各种添加剂可以实现这种转化。讨论了不同方案的范围和局限性,并基于31 P和1 H NMR光谱学研究提出了一些机械方面的考虑。
Regioselectivity Influences in Platinum-Catalyzed Intramolecular Alkyne O–H and N–H Additions
作者:Jeff P. Costello、Eric M. Ferreira
DOI:10.1021/acs.orglett.9b03557
日期:2019.12.20
The steric and electronic drivers of regioselectivity in platinum-catalyzed intramolecular hydroalkoxylation are elucidated. A branch point is found that divides the process between 5-exo and 6-endo selective processes, and enol ethers can be accessed in good yields for both oxygen heterocycles. The main influence arises from an electronic effect, where the alkyne substituent induces a polarization
A nitrite-catalyzed ring contraction reaction of substituted tetrahydrofurans by oxidation of bromide under aerobic conditions as a dehydrogenative dual functionalization was developed to provide 2-acyltetrahydrofurans in good yields. On the other hand, the oxidation reaction of 1-substituted isochromans occurred via the bromohydroxylation to give 1-(dibromoalkyl)-1-hydroxyisochromans in high yields
We have developed a nickel-catalyzedcross-coupling reaction of cyclic alkenyl ethers with arylboronic esters that leads to the formation of unsaturated alcohols via ring-opening by the cleavage of a C(sp2)–O bond. The use of 1,3-dicyclohexylimidazol-2-ylidene as the ligand is essential to promote this cross-coupling process.
ω-Acyloxy n-butylidenetriphenylphosphoranes give α-acyl n-butylidenetriphenylphosphoranes by intermolecular condensation in t-BuOH, and 3,4-dihydro-(2H)-pyrans by intramolecular condensation in toluene. The α-acyl n-butylidene phosphoranes, which are the tautomeric form of α-acyloxaphosphanes, do not lead to cyclobutylketones but to dihydropyrans.