Environment-friendly organic synthesis using bismuth compounds. Bismuth triflate catalyzed synthesis of substituted 3,4-dihydro-2H-1-benzopyrans

A highly catalytic method for the synthesis of dihydrobenzopyrans from salicylaldehydes has been developed. An extension of this method to the synthesis of a pyrano[2,3,b]benzopyran has also been achieved. Bi(OTf)₃·xH₂O (1 < x < 4) (0.1 mol%) smoothly catalyzes the condensation of substituted salicylaldehydes with 2,2-dimethoxypropane to give the corresponding substituted 3,4-dihydro-2H-1-benzopyrans as a mixture of diastereomers (9:1) in moderate yields. The relative configuration of the methoxy groups in the two diastereomers was established by NOE experiments. The advantages of this method include the use of an easy to handle, inexpensive and relatively non-toxic catalyst.     

Bismuth compounds in organic synthesis. A one-pot synthesis of homoallyl ethers and homoallyl acetates from aldehydes catalyzed by bismuth triflate

[reaction: see text] Three one-pot methods for the conversion of aldehydes to homoallyl ethers catalyzed by Bi(OTf)(3).xH(2)O (1 < x < 4) have been developed. The one-pot synthesis of homoallyl ethers can be achieved either by in situ generation of the acetal followed by its reaction with allyltrialkylsilane or by a three-component synthesis in which the aldehyde, trimethylorthoformate or an alkoxytrimethylsilane and allyltrimethylsilane are mixed together in the presence of bismuth triflate (0.1-1.0 mol %). In addition, a three-component synthesis of homoallyl acetates, which is achieved by reacting the aldehyde, acetic anhydride, and allyltrimethylsilane in the presence of bismuth triflate (3.0-5.0 mol %), has been developed. The use of a relatively nontoxic, easy to handle, and inexpensive catalyst adds to the versatility of these methods.     

A practical and efficient procedure for the cleavage of acylals to aldehydes catalyzed by indium tribromide in water

Indium tribromide (10 mol %) is an efficient catalyst for chemoselective cleavage of aryl acylals in refluxing water. A variety of acylals have been deprotected to give the corresponding parent aldehydes in high yield. The procedure presented is operationally simple, practical, and compatible with other sensitive functionalities such as methoxy, methyleneioxy, and benzyloxy groups present in the substrates.     

Bismuth nitrate-catalyzed novel synthesis of pyrrole-substituted indolinones

Synthesis of indole derivatives bound to pyrroles is a challenge. In this letter, an expeditious synthesis of these types of molecules starting from isatins and 4-hydroxy proline via a bismuth nitrate-catalyzed reaction is described.     

Silica-supported ceric ammonium nitrate catalyzed chemoselective formylation of indoles

Selective formylation of free (N–H) indoles at C3 can be achieved by using formylating species generated from hexamethylenetetramine (HMTA) and silica-supported ceric ammonium nitrate (CAN–SiO₂). The use of a catalytic amount of this solid-supported reagent was found to be compatible with a range of substituents on the indoles and generated the corresponding products with good yields. A plausible mechanism for the formylation involving an electron transfer process is discussed.     

Three-component synthesis of amidoalkyl naphthols catalyzed by bismuth(III) nitrate pentahydrate

Bismuth(Ⅲ) nitrate pentahydrate catalyzed the three-component condensation ofβ-naphthol,aldehydes and amines/urea under solvent-free conditions to afford the corresponding amidoalkyl naphthols in excellent yields.     

Three components synthesis of homoallylic amines catalyzed by bismuth(III) nitrate pentahydrate

Bismuth (III) nitrate pentahydrate catalyzes efficiently the three-component condensation of aldehydes, amines, and allyltributylstannane at rt to afford the corresponding homoallylic amines in excellent yield.     

Bismuth triflate catalyzed condensation of δ-hydroxy-α,β-unsaturated aldehydes with aryl amines

α,β-Unsaturated aldehydes bearing a δ-hydroxyl group undergo a tandem Michael and intramolecular Friedel-Crafts type cyclization with arylamines in the presence of 5 mol % of Bi(OTf)₃ under mild conditions to afford a new class of chiral tetrahydroquinolines in good yields with high stereoselectivity. Structural assignments and the stereochemistry of the products was achieved using various 1D and 2D-NMR experiments.     

An efficient and versatile synthesis of aromatic nitriles from aldehydes

A simple and direct method has been developed for synthesis of nitriles based on one-pot reaction of aromatic aldehydes with three different kind of reagents:CeCl₃7H₂O/KI/H₂O₂,CeCl₃·7H₂O/KI/UHP and（NH₄）₂Ce（NO₃）₆/KI/H₂O₂ in aqueous ammonia.     

Environment friendly organic synthesis using bismuth compounds. An efficient method for carbonyl-ene reactions catalyzed by bismuth triflate

Bismuth triflate (0.1 mol %) is a highly efficient catalyst for the cyclization of citronellal 1, a reaction that yields a ratio of 80:20 of isopulegol 2 and neoisopulegol 3. This methodology has also been extended to the synthesis of substituted piperidines. The bismuth triflate catalyzed ene reaction of aldehyde 4 gives a 70:30 mixture of piperidines 5 and 6. The advantages of these methods include the use of a highly efficient catalyst that is relatively nontoxic, cheap and easy to handle.     

Environmentally friendly organic synthesis using bismuth compounds: bismuth(III) iodide catalyzed deprotection of acetals in water

The chemoselective deprotection of a wide range of acetals and ketals in water is catalyzed by bismuth(III) iodide. Bismuth(III) compounds are remarkably nontoxic and hence are attractive as environmentally friendly catalysts.     

An efficient method for the synthesis of acylals from aldehydes using silica-supported perchloric acid (HClO4-SiO2)

The synthesis of acylals from structurally diverse aldehydes has been performed in excellent yields under solvent-free conditions using HClO₄-SiO₂ as a mild, convenient, reusable, and heterogeneous catalyst. The procedure is operationally simple, environmentally benign and has the advantage of enhanced atom utilization. Furthermore, the catalyst can be recovered simply and reused efficiently a number of times without appreciable loss of activity.     

Bismuth compounds in organic synthesis. Synthesis of resorcinarenes using bismuth triflate

Bismuth triflate (5 mol%) smoothly catalyzes the condensation of aromatic and aliphatic aldehydes with resorcinol to give tetrameric cyclic products, resorcinarenes. With benzaldehyde, the product is obtained as a mixture of two diastereomers and the ratio of the diastereomers depends on reaction time. On the other hand, a single diastereomer is obtained with aliphatic aldehydes. The low toxicity and ease of handling of bismuth compounds coupled with fast reaction times make this method an attractive alternative to the existing methods for resorcinarene formation.     

Bismuth compounds in organic synthesis. Deprotection of ketoximes using bismuth bromide-bismuth triflate

Ketoximes undergo deprotection in CH₃CN/acetone/H₂O (3:6:1) in the presence of 20-40 mol% BiBr₃/5 mol% Bi(OTf)₃. Bismuth(III) salts are relatively non-toxic, insensitive to air and inexpensive. These features coupled with the use of a relatively non-toxic solvent system make this method an attractive alternative to existing routes for deprotection of ketoximes.     

Catalyst free,base free microwave irradiated synthesis of aryl nitrites from potassium aryltrifluoroborates and bismuth nitrate

A mixture of bismuth nitrate pentahydrate and potassium aryltrifluoroborate in toluene under microwave heating at 120 °C for 20 min provides an interesting and mild reaction protocol for the synthesis of aryl nitrite. The conversion to aryl nitrites from aryltrifluoroborates without transition metal catalyst and base in high yields is remarkable.     

Bismuth(III) bromide in organic synthesis. A catalytic method for the allylation of tetrahydrofuranyl and tetrahydropyranyl ethers

A bismuth bromide-catalyzed (10.0 mol %) multicomponent reaction involving the allylation of THF- and THP-ethers, followed by in situ derivatization with acetic anhydride to generate highly functionalized esters has been developed under solvent-free conditions. To the best of our knowledge, this is the first report of a catalytic procedure for the allylation of THF- and THP-ethers to yield ring-opened products.     

Cobalt(II)-catalyzed chemoselective synthesis of acetals from aldehydes

The acetalization of aldehydes has been studied with methanol, ethanol, and 2-propanol using CoCl₂ in high yields under reflux conditions. The reaction is simple, efficient, chemoselective and does not involve any other additive.     

Convenient synthesis of non-conjugated alkynyl ketones from keto aldehydes by a chemoselective one-pot nonaflation—base catalyzed elimination sequence

Keto aldehydes were selectively converted to non-conjugated alkynyl ketones possessing an unsubstituted alkyne terminus using one-pot nonaflation—base catalyzed elimination reaction sequences. Consecutive one-pot nonaflation of keto aldehydes with perfluorobutane-1-sulfonyl fluoride and elimination of the nonaflyl group using the P₁ phosphazene base resulted in the formation of a terminal CC triple bond with the keto group remaining intact. Careful optimization of the reaction conditions enabled a highly chemoselective conversion of the aldehyde function in the presence of unprotected keto groups exploiting a minor difference in acidity of their α-hydrogen atoms. Scope and limitations of the protocol as well as possible implementation of these substrates in Sonogashira coupling were explored.     

Facile one-pot clean synthesis of benzimidazole motifs: Exploration on bismuth nitrate accelerated subtle catalysis

In the present letter, an efficient, clean and one-pot synthesis of 2-substituted benzimidazole and 1,2-disubstituted benzimidazole derivatives has been explored by reacting o-phenylenediamine with aromatic aldehydes using bismuth nitrate as a catalyst in ethanol at ambient temperature. This methodology avails with faster reactions, excellent yield, mild reaction conditions, use of inexpensive and non-toxic catalyst compared to literature reported hitherto.     

聚氯乙烯支载三氯化铁试剂催化醛与乙酸酐反应合成 乙酰缩醛

聚氯乙烯支载三氯化铁(PVC-FeCl3)试剂在室温条件下能方便快速催化各类醛与乙酸酐反应,以良好产率(75%～96%)生成相应乙酰缩醛。