5980-96-1Relevant articles and documents
Preparation of the novel mesoporous solid acid catalyst UDCaT-4 via synergism of persulfated alumina and zirconia into hexagonal mesoporous silica for alkylation reactions
Yadav, Ganapati D.,Murkute, Ambareesh D.
, p. 389 - 394 (2004)
A novel mesoporous solid acid catalyst named UDCaT-4 was designed by loading persulfated alumina and zirconia (PAZ) into highly oredered, hexagonal mesoporous silica (HMS). UDCaT-4 was characterized by XRD, BET surface area and pore size analysis which revealed that neither pore blocking nor structure collapse of HMS had occurred. NH3-TPD and FTIR were used to determine the acid strength and nature of the sulfate ion retained on the surface of UDCaT-4. It is known that HCl and water have detrimental effects on the activity of the zirconia-based catalyst. Hence, the activity of UDCaT-4 was evaluated in comparsion with that of bulk PAZ in the liquid-phase alkylation of toluene with benzyl chloride and also in the vapour-phase alkylation of mesitylene with isopropanol, where acid and water are generated in-situ, respectively, as co-products. The superior catalytic acivity of UDCaT-4 is atributed to the uniform dispersion of the superacidic centers of PAZ into HMS vis-a-vis bulk PAZ. Reusability and time on-stream studies reveal that UDCaT-4 is a robust and reusable catalyst even in the presence of HCl and H2O.
Efficient cross-coupling of aryl/alkenyl triflates with acyclic secondary alkylboronic acids
Si, Tengda,Li, Bowen,Xiong, Wenrui,Xu, Bin,Tang, Wenjun
supporting information, p. 9903 - 9909 (2017/12/12)
Aryl-secondary alkyl cross-coupling with aryl sulfonate esters as coupling partners remains a significant challenge. Efficient cross-coupling between aryl/alkenyl triflates and acyclic secondary alkylboronic acids is realized for the first time to provide a series of sterically congested acyclic secondary alkyl arenes/olefins in good to excellent yields. The employment of sterically bulky P,PO ligand L1/L2 is crucial for the high yields and selectivities. The method has enabled a concise and 4-step synthesis of a key intermediate of male contraceptive agent and PAF antagonist gossypol.
Palladium-catalysed direct cross-coupling of secondary alkyllithium reagents
Vila, Carlos,Giannerini, Massimo,Hornillos, Valentin,Fananas-Mastral, Martin,Feringa, Ben L.
, p. 1361 - 1367 (2014/03/21)
Palladium-catalysed cross-coupling of secondary C(sp3) organometallic reagents has been a long-standing challenge in organic synthesis, due to the problems associated with undesired isomerisation or the formation of reduction products. Based on our recently developed catalytic C-C bond formation with organolithium reagents, herein we present a Pd-catalysed cross-coupling of secondary alkyllithium reagents with aryl and alkenyl bromides. The reaction proceeds at room temperature and on short timescales with high selectivity and yields. This methodology is also applicable to hindered aryl bromides, which are a major challenge in the field of metal catalysed cross-coupling reactions.
