Solvent-free preparation of primary carbamates using silica sulfuric acid as an efficient reagent

Abstract

A simple and efficient method for the conversion of structurally diverse compounds containing a hydroxyl group to primary carbamates is described by grindstone chemistry. The transformation was done at room temperature with high yield and purity, and without any epimerization in the absence of solvent. Silica sulfuric acid was used as a solid acid and as a mild, convenient and effective reagent for this transformation.

Synthesis of Thiotetrazoles and Arylaminotetrazoles Using Rutile Tio2 nanoparticles as a heterogeneous and reusable catalyst

“…To show the merits of rutile TiO 2 nanoparticles in comparison with other reported catalysts, we summarised some of results in Scheme 2, which show that rutile TiO 2 is an equally or more efficient catalyst with respect to reaction time and yield than those previously reported. As shown in Scheme 2, a rutile TiO 2 nanoparticle is an effective catalyst since the products are regiospecific, whereas with hydrazoic acid, 16 FeCl 3 -SiO 2 17 and glacial acetic acid, 7 a mixture of isomers are produced. If hydrazoic acid is used, care must be taken by monitoring the concentration of hydrazoic acid in the reaction mixture to avoid an explosion.…”

“…[1][2][3][4][5][6] Tetrazoles are conventionally synthesised by the reaction of harmful hydrazoic acid or azide ions with nitriles, thiocyanates or cyanamides in the presence of homogeneous catalysts. [3][4][5][6][7][8][9][10][11] However, these procedures suffer from disadvantages such as environmentally unpleasant use of toxic reagents or stoichiometric amounts of homogeneous mediators, long reaction times, harsh reaction conditions, tedious isolation steps and low yields of the products. This has limited the largescale applications of tetrazoles in industry.…”

Silica supported Brönsted acids as catalyst in organic transformations: A comprehensive review

“…Modarresi-Alam et al [84] synthesized primary carbamates using silica sulphuric acid. Primary carbamates were prepared in high yields and in high purity from the reaction of either alcohol or phenol with sodium cyanate in the presence of SSA at room temperature or 55-65 °C for an appropriate time.…”

“…Menthyl, CH 3 CH 2 , CH 3 CH 2 CH 2 , C 6 H 11 , (CH 3 ) 3 C, PhCH 2 , (CH 3 ) 2 CH0CH 2 CH 2 , CH 2 =CHCH 2 , C 6 H 5 , 4-CH 3 C 6 H 4 , 4-BrC 6 H 4 , 2-C(CH 3 ) 3 -4-CH 3 C 6 H 4 , α-naphthyl, β-naphthyl Scheme 78. Synthesis of primary carbamates using silica sulphuric acid by[84].…”

CoFe2O4 Nanoparticles as a Magnetically Recoverable and Reusable Catalyst for the Synthesis of Arylaminotetrazoles and 5-aryloxytetrazoles

“…There has been an interest in various chemical transformations performed with heterogeneous catalysis [20][21][22][23][24] and, in particular, magnetic nanoparticles have emerged as a useful group. [25][26][27][28][29][30] The separation of magnetic nanoparticles is simple, and an attractive alternative to filtration or centrifugation as it prevents the loss of catalyst and enhances reusability, making the catalyst more cost-effective and promising for industrial applications. Recently, magnetically separable CoFe 2 O 4 nanoparticles, have been prepared by a simple procedure and their catalytic activity investigated.…”