Y(OTf)3-Catalyzed Cascade Propargylic Substitution/Aza-Meyer–Schuster Rearrangement: Stereoselective Synthesis of α,β-Unsaturated Hydrazones and Their Conversion into Pyrazoles
concise method for the highly stereoselective synthesis of α,β-unsaturated hydrazones by the Y(OTf)3-catalyzed cascade propargylic substitution/aza-Meyer–Schuster rearrangement reaction of tertiary propargylic alcohols and p-toluenesulfonyl hydrazide under an air atmosphere is developed. A series of α,β-unsaturated hydrazones have been synthesized from simple and readily available starting materials
Perfluoro-tagged, phosphine-free palladium nanoparticles supported on silica gel: application to alkynylation of aryl halides, Suzuki–Miyaura cross-coupling, and Heck reactions under aerobic conditions
cross-coupling, as well as in the Heck reaction between methyl acrylate and aryl iodides is described. The reactions are carried out under aerobic and phosphine-free conditions with excellent to quantitative product yields in each case. The catalysts are easily recovered and reused several times without significant loss of activity. The alkynylation of aryl halides (under copper-free conditions) and the Suzuki–Miyaura
Polymethylhydrosiloxane (PMHS) as an Additive in Sonogashira Reactions
作者:Robert E. Maleczka Jr.、William P. Gallagher
DOI:10.1055/s-2003-37522
日期:——
Polymethylhydrosiloxane (PMHS) in combination with CsF facilitates the Sonogashira reaction of a variety of alkynes and electrophiles. These couplings appear to involve the in situ formation and reaction of an alkynylsiloxane. Such couplings can be run amine free at room temperature, reaction times are short, workup is easy, and product purification is straightforward. Thus, the advantages (and disadvantages) of running Sonogashira couplings with 1-silylalkynes are realized, without the need to preform the alkynyl silane.
Alkynylation of aryl halides with perfluoro-tagged palladium nanoparticles immobilized on silica gel under aerobic, copper- and phosphine-free conditions in water
The utilization of perfluoro-tagged palladium nanoparticles immobilized on fluorous silica gel through fluorous–fluorous interactions (Pdnp-A/FSG) or linked to silica gel by covalent bonds (Pdnp-B) in the alkynylation of terminal alkynes with aryl halides under aerobic, copper- and phosphine-free conditions in water, and their recovery and re-utilization, is described.
An acid catalysed, cascade process for the construction of angularly fusedpolycyclic phthalides from isobenzofurans under transition metal free conditions has been reported. This process is very general for diverse gem-disubstituted isobenzofuran substrates. Control experiments supported the mechanism as the nucleophilic attack of the carboxylate onto the acid activated furan ring for the simultaneous