synthesized through regio- and stereoselective iodo(III)functionalization of alkynes. The combination of chlorobenziodoxole and silver salt has proven to generate a versatile cationic iodine(III) electrophile to activate alkynes and engage various carboxylic acids, triethyl phosphate, and p-toluenesulfonic acid as nucleophiles. The β-iodo(III)enol esters serve as starting materials for the synthesis of multisubstituted
Indirect Electroreductive Sequential Radical Reaction Catalyzed by a Ni(II) Complex. One-Step Preparation of Functionalized (Methylene)cyclopentanes.
作者:Shigeko OZAKI、Shizue MITOH、Hidenobu OHMORI
DOI:10.1248/cpb.43.1435
日期:——
Substituted (methylene)cyclopentanes were prepared by one-step reaction at room temperature from butynyl iodides and activated olefins by sequencing of free radical addition and cyclization reactions. The reactions, which were conducted by indirect electroreduction catalyzed by a nickel(II) complex, proceeded with modest selectivity for formation of the Z(methylene)cyclopentanes.
The synthesis of pyridines through direct intermolecular cycloaddition of alkynes and nitriles is a contemporary challenge in organic synthesis. A Brønsted acid mediated formal [2+2+2] cycloaddition of heteroalkynes and nitriles was developed that proceeds under mild conditions. This constitutes a modular approach to highly substituted pyridine cores.
Nitriles were activated in presence of Tf2O into aza-allene species followed by an intermolecular / intramolecular [2+2+2] cycloaddition. This process was evidenced by detailed deuteration experiments and competing reactions. A bidentate pyrimidine ligand was synthesized for preparation of a metal complex with pure blue luminescence at 470 nm.
Metal-Free [2+2+2] Cycloaddition of Ynamides and Nitriles: Mild and Regioselective Synthesis of Fully Substituted Pyridines
作者:Yong Wang、Li-Juan Song、Xinhao Zhang、Jianwei Sun
DOI:10.1002/anie.201603889
日期:2016.8.8
A metal‐free trimolecular [2+2+2] cycloaddition of internal ynamides and nitriles for de novo synthesis of fully substituted pyridines is disclosed. With the versatile Brønsted acid catalyst HNTf2, the mild intermolecular cyclotrimerization process proceeds with complementary chemoselectivity and excellent regioselectivity.