已开发出一种无金属的非均相光催化系统,用于使用氧气作为氧化剂的高效苄基CH氧化。这种可见光介导的氧化反应利用石墨碳氮化物(gC 3 N 4)作为可回收,无毒且低成本的光催化剂。温和的反应条件可从易于获得的烷基芳族前体中以高收率生成合成和生物学上有价值的异苯并二氢醌,邻苯二甲酸,异喹啉酮,异吲哚啉酮和氧杂蒽。gC 3 N 4的异质性催化系统可轻松回收和循环利用,并可多次使用而不会损失活性。通过在生物活性和具有药物价值的靶标合成中的应用,进一步证明了这种“绿色”方法的综合效用。
A ligand-free iron-catalyzed method for the oxygenation of benzylic sp3 C–H bonds by molecular oxygen (1 atm) using a thiylradical as a cocatalyst has been developed. This transformation provides a facile access to amides, esters and ketones from readily accessible corresponding amines, ethers and alkanes. It features high regioselectivity, mild oxidative conditions and excellent functional group
A ligand-free and operationally simple copper-catalyzed aerobic benzylic sp3 C–H oxygenation was developed. The addition of tert-butyl hydroperoxide, either in a catalytic or stoichiometric amount, was key for activating stable C–H bonds under mild conditions to furnish the corresponding ketones or esters in moderate to excellent yield.
Enantioselective Copper(I)-Catalyzed Alkynylation of Oxocarbenium Ions to Set Diaryl Tetrasubstituted Stereocenters
作者:Srimoyee Dasgupta、Thomas Rivas、Mary P. Watson
DOI:10.1002/anie.201507373
日期:2015.11.16
An enantioselective, copper(I)-catalyzed addition of terminal alkynes to isochroman ketals to setdiaryl, tetrasubstitutedstereocenters has been developed. The success of this reaction relies on identification of a Cu/PyBox catalyst capable of distinguishing the faces of the diaryl-substituted oxocarbeniumion. This challenging transformation enables efficient conversion of readily available, racemic
New Synthetic Methods for Seven- and Eight-Membered Cyclic Ethers Based on the Ring-Expansion Reactions of Hydroxy or Lithioxy Methoxyallenylisochroman Derivatives
The Pd(0)-catalyzed ring-expansion reactions of hydroxy methoxyallenyl-4,4-dialkylisochroman derivatives in the presence of P(o-tolyl) 3 proceeded smoothly via hydropalladation to give 3-benzoxepan-1-one derivatives in high yields. Treatment of isochroman-1-one derivatives with lithio methoxyallene followed by quenching the reaction with water furnished 3-benzoxocan-6-one derivatives in good yields
α-Angelica lactone catalyzed oxidation of benzylic sp<sup>3</sup> C–H bonds of isochromans and phthalans
作者:Thanusha Thatikonda、Siddharth K. Deepake、Pawan Kumar、Utpal Das
DOI:10.1039/d0ob00729c
日期:——
efficient benzylic C–H oxygenations of cyclic ethers using oxygen as an oxidant. This oxidation reaction utilizes α-angelica lactone as a low cost/low molecular weight catalyst. The optimized reaction conditions allow the synthesis of valued isocoumarins and phthalides from readily available precursors in good yields. Mechanistic studies indicate that the reaction pathway likely involves a radical process