6948-68-1Relevant articles and documents
Direct deoxygenation of active allylic alcohols via metal-free catalysis
Han, Feng,Ji, Na,Liu, Qiaowen,Miao, Chengxia,Zhang, Tong,Zhuang, Hongfeng
, p. 1680 - 1689 (2022/03/02)
Direct metal-free deoxygenation of highly active allylic alcohols catalyzed by a Br?nsted acid was achieved, which avoids tedious reaction steps and eliminates metal contamination. By examining a series of Br?nsted acids, alcohols, reaction temperatures and so on, up to 94% yield was obtained with 10 mol% TsOH·H2O as the catalyst and 2 equiv. of p-methylbenzyl alcohol as the reductant at 80 °C for 2 h. The system was mainly suitable for aromatic allylic alcohols, and the yield was excellent as determined via gram-scale synthesis. The main product was double bond near the side of a more electron-rich aryl group when allylic alcohols featuring different substituents at the 1 and 3 positions were used as the substrates. Deuterium-labelled experiments clearly demonstrated that the hydrogen source was the methylene of p-methylbenzyl alcohol and other control experiments indicated the existence of two ether intermediates. Interestingly, in situ hydrogen transfer of allylic benzyl ether is a key process, but kinetic isotopic effect studies (kH/kD = 1.28) showed that the C-H bond cleavage was not the rate-determining step. A possible mechanism involving carbocations, ether intermediates and hydrogen transfer is proposed.
Influences of Phenyl Rings on NHC Ligands with Bicyclic Architectures
Ando, Shin,Miyata, Ryota,Matsunaga, Hirofumi,Ishizuka, Tadao
, p. 128 - 139 (2019/01/04)
In addition to phosphanes, olefins, amines, and amides, over the past two decades N-heterocyclic carbene (NHC) has emerged as a useful alternative ligand. Based on a number of derivatization studies on NHC ligands, imidazol-2-ylidene and imidazolin-2-ylidene became the standard heterocyclic form, and bulky substituents have commonly been introduced on the nitrogen(s) adjacent to carbenic carbons. Our group previously developed NHCs equipped with noncarbenic carbons with a bicyclic architecture that gives them unique steric properties that make them bulky but accessible. In this study, we synthesized a novel type of NHC ligand that possesses a bicyclo[2.2.1]heptane architecture, and we compared five derivatives using copper-catalyzed allylic arylations with aryl Grignard reagents. The regioselectivity of the substitution obviously indicates that a phenyl ring over an active site has a characteristic effect on the resultant copper catalysts when γ-substitution is the major pathway.
Catalytic allylic arylation of cinnamyl carbonates over palladium nanoparticles supported on a thermoresponsive polymer in water
Lee, Yongwoo,Shabbir, Saira,Lee, Sinyoung,Ahn, Hyunsoek,Rhee, Hakjune
, p. 3579 - 3583 (2015/06/25)
Poly(NIPAM-co-4-VP) undergoes a phase transition at the low critical solution temperature with a change from the hydrophilic to the hydrophobic core in a hydrophilic solvent. Palladium nanoparticles supported on such a thermoresponsive polymer support were demonstrated to catalyze the Tsuji-Trost reaction for the arylation of various cinnamyl carbonates by arylboronic acids. Therefore, a protocol developed using mild reaction conditions demonstrates the recyclability of the catalyst in an eco-friendly solvent such as water.
