1268161-16-5Relevant articles and documents
Transition-Metal-Free Cross-Coupling of Indium Organometallics with Chromene and Isochroman Acetals Mediated by BF3·OEt2
Gil-Negrete, José M.,Sestelo, José Pérez,Sarandeses, Luis A.
supporting information, p. 4316 - 4319 (2016/10/12)
A transition-metal-free coupling of triorganoindium reagents with benzopyranyl acetals mediated by a Lewis acid has been developed. The reaction of R3In with chromene and isochroman acetals in the presence of BF3·OEt2 afforded 2-substituted chromenes and 1-substituted isochromans, respectively, in good yields. The reactions proceed with a variety of triorganoindium reagents (aryl, heteroaryl, alkynyl, alkenyl, alkyl) using only 50 mol % of the organometallic, thus demonstrating the efficiency of these species. Preliminary mechanistic studies indicate the formation of an oxocarbenium ion intermediate in the presence of the Lewis acid.
Synergistic gold(I)/trimethylsilyl catalysis: Efficient alkynylation of N,O-acetals and related pro-electrophiles
Michalska, Malina,Songis, Olivier,Taillier, Catherine,Bew, Sean P.,Dalla, Vincent
supporting information, p. 2040 - 2050 (2014/07/07)
We report a unique mechanism-guided reaction that enhances and expands the chemical space that readily generated gold(I) acetylides currently operate in. Our strategy exploits the propensity of gold(I) carbophilic catalysts with specific counteranions (LAuX - X=triflate or triflimidate) to efficiently activate and desilylate trimethylsilylalkynes, thereby mediating the in situ formation of equal and catalytic quantities of a silyl Lewis acid (TMSX) of tunable strength and a nucleophilic gold(I) acetylide. This unprecedented manifold opens avenues for developing synergistic silyl-gold(I)-catalyzed alkynylation strategies of diverse pro-electrophiles which were heretofore unattainable, the proof of concept being principally exemplified herein with the first catalytic alkynylation of N,O-acetals. The reaction proceeds at low catalyst loading, employs mild reaction conditions, is easily scalable, and affords propargylic lactam products in good to excellent yields. Furthermore, it is fully amenable to a diverse array of structure and function substrates, and also expands to other pro-electrophiles beyond N,O-acetals. Control experiments have been carried out that strongly support our dual reaction mechanism proposal which, furthermore, itself outlines an inextricable link between the strength of the ancillary silyl Lewis acid (TMSOTf versus TMSNTf2) and the coordinating ability of the gold counter anion employed. This underlying feature of our system underscores its significant potential and flexibility, which indeed manifests with the demonstration that by carefully selecting the gold counter ion, it is possible to manipulate the strength of the ancillary silyl Lewis acid so that it can be tailored to the ionizing ability of a particular pro-electrophile.
Practical and highly selective C-H functionalization of structurally diverse ethers
Wan, Miao,Meng, Zhilin,Lou, Hongxiang,Liu, Lei
supporting information, p. 13845 - 13849 (2015/01/16)
A trityl ion mediated C-H functionalization of ethers with a wide range of nucleophiles at ambient temperature has been developed. The reaction displays high chemo-selectivity and good functional group tolerance. The protocol also exhibits excellent regio- and diastereoselectivities for the unsymmetric ethers, thus stereoselectively generating highly functionalized disubstituted 2,5-trans tetrahydrofurans (THF), 2,6-trans tetrahydropyrans (THP), 2,6-trans dihydropyrans (DHP), and 1,3-trans isochromans, and highlighting the capacity of the protocol in complex molecule synthesis.
