Abstract:It is reported that Ga(OTf)(3) catalyzes the direct displacement of alcohols with sulfur nucleophiles. The products are versatile intermediates that can be utilized in carbon-carbon, carbon-sulfur bond formation or used in modified Julia olefination reactions. The only byproduct generated is water.
“…[28] Wu group also successfully realized the direct displacement of alcohols with sulfur nucleophiles catalyzed by Ga(OTf ) 3 . [29] Based on the systems, we found thiolation of alcohols could be carried out well with simple Lewis or Brønsted acids as the catalysts. However, these catalysts could not be recycled and separated easily with the product.…”
Thioethers as important building blocks have been usually found in organic synthesis. Herein, a series of long chained acid‐functionalized ionic liquids derived from pyrrolidine were applied for the thiolation of alcohols to synthesize different compounds containing thioether structures. This kind of ionic liquids exhibited higher efficiency than general ionic liquids based on imidazole, providing up to 99 % yield with [BsCtP][OTf] as the catalyst at room temperature for 0.25 h. The results indicated that the activities of the ionic liquids have relationship with the side chain length of ionic liquids based on pyrrolidine, anions and cations. The catalytic system had wide substrate scope and was applicable for the reaction of aromatic primary and secondary alcohols and thiols including aliphatic and aromatic thiols, benzothiazole‐2‐thiols and benzooxazole‐2‐thiols. Besides, there was no obvious change in activity of the catalyst after six runs. Thus, the catalytic system exhibited good recyclability. Additionally, carbocations should be the key intermediate and several functionalized groups of the ionic liquids have synergetic effect for the thiolation.
“…[28] Wu group also successfully realized the direct displacement of alcohols with sulfur nucleophiles catalyzed by Ga(OTf ) 3 . [29] Based on the systems, we found thiolation of alcohols could be carried out well with simple Lewis or Brønsted acids as the catalysts. However, these catalysts could not be recycled and separated easily with the product.…”
Thioethers as important building blocks have been usually found in organic synthesis. Herein, a series of long chained acid‐functionalized ionic liquids derived from pyrrolidine were applied for the thiolation of alcohols to synthesize different compounds containing thioether structures. This kind of ionic liquids exhibited higher efficiency than general ionic liquids based on imidazole, providing up to 99 % yield with [BsCtP][OTf] as the catalyst at room temperature for 0.25 h. The results indicated that the activities of the ionic liquids have relationship with the side chain length of ionic liquids based on pyrrolidine, anions and cations. The catalytic system had wide substrate scope and was applicable for the reaction of aromatic primary and secondary alcohols and thiols including aliphatic and aromatic thiols, benzothiazole‐2‐thiols and benzooxazole‐2‐thiols. Besides, there was no obvious change in activity of the catalyst after six runs. Thus, the catalytic system exhibited good recyclability. Additionally, carbocations should be the key intermediate and several functionalized groups of the ionic liquids have synergetic effect for the thiolation.
“…Following this work, Wu and co-workers reported the formation of thiol compounds from benzylic alcohols and sulfur nucleophiles via Ga(OTf) 3 catalyzed direct nucleophilic substitution, which was much more convenient compared to the traditional Mitsunobu reaction (Table 1.9, entry 8). 78 In this work, phosphorothioic acid 102, phenyltetrazole 103, and other heteroaromatic thiols 104 and 105 were shown to be as efficient nucleophiles that afforded the corresponding sulfides products in up to 94% yield, which were very useful due to their application in the preparation of sulfones and Julia olefination reactions.…”
The work of this thesis has been directed toward establishing new Lewis and Brønsted acid-catalyzed reactions of alcohol pro-electrophiles as novel synthetic strategies for C−X (X = C, N, O, S) bond formation. This thesis is divided into three parts: Part I consists of Chapter I, which gives an introduction of Lewis and Brønsted acid catalyzed reactions of alcohol pro-electrophiles, particularly those containing a pendant activated alcohols such as allylic, propargylic, benzylic and cyclopropylmethyl functional group. Part II describes the new strategies developed for C−X (X = C, N, O, S) bond formation employing alcohols as pro-electrophiles. Chapter II reports iron(III) chloride catalyzed direct nucleophilic α-substitution of Morita-Baylis-Hillman alcohols with alcohols, arenes, 1,3-dicarbonyl compounds, and thiols. In Chapter III, a new method to indenols that relied on ytterbium(III) triflate catalyzed tandem Friedel-Crafts arylation/hydroarylation of propargylic alcohols with phenols is described. Chapter IV detailed the synthesis of highly substituted indene derivatives via Brønsted acid catalyzed intramolecular Friedel-Crafts cyclization of homoallylic alcohols. In Chapter V, a novel strategy to di-and trisubstituted thiazoles via Brønsted acid catalyzed cyclization of propargylic alcohols with thioamides was described. Chapter VI Chapter I. Alcohol Pro-electrophiles in Lewis and Brønsted Acid Catalysis
“…Phenols Access to dihydrobenzofuran-appended oxindoles, a common motif in a variety of natural products, may be realized through a Ga(OTf) 3 -catalyzed reaction between allenols and phenols (25). 32 The simultaneous interaction of Ga(OTf) 3 with the allene and phenol moieties was proposed with the formation of a Ga(π-allene) phenolate species.…”
Section: Domino Arylation/oxycyclization Of Allenes Withmentioning
The present contribution highlights the most recent and representative developments on the use of Ga and In species in homogeneous catalysis. Recent studies of various ligand‐supported Ga(III) and In(III) compounds in cyclic esters polymerization catalysis for the production of biodegradable polyester materials are also included. Various organic transformations may now be catalyzed using Ga(III) and In(III) Lewis acids allowing access to a wide range of valuable organic molecules through diverse reaction sequences. The recent use of stable and robust
N
‐heterocyclic carbene Ga(III) and In(III) compounds as strong π‐Lewis acid catalysts for various organic reactions is also discussed: such species are certainly promising for the future developments of Ga(III)‐ and In(III)‐mediated reactions. Although Lewis acid‐assisted reactions certainly dominate the field in Ga(III) and In(III) chemistry, discrete low‐valent In(I) species, presently emerging in catalysis, clearly display a distinct reactivity allowing their exploitation both as soft Lewis acids and alkyl‐/allyl‐/arylating agents.
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