Dehydration of alcohols catalyzed by copper(II) sulfate adsorbed on silica gel

Copper(II) sulfate adsorbed on silica gel efficiently dehydrated secondary and tertiary alcohols under mild conditions to give olefins. The rate of dehydration of tertiary alcohols is much faster than that of secondary alcohols.     

Dehydration of ethylenic alcohols

Summary A systematic study was made of the catalytic dehydration of 4-methyl-1-penten-3-ol (Ia), 3,4-dimethyl-1--penten-3-ol (Ib), 3-isopropyl-4-methyl-1-penten-3-ol (Ic), 2-methyl-4-penten-2-ol (II), 2-methyl-3-penten-2-ol (III), 4-methyl-3-penten-2-ol (IV), and 2-methyl-4-hexen-3-ol (V). In the course of this study methods were developed for the preparation of the following substituted gem-dimethylbutadienes: 4-methyl-1,3-pentadiene (VIII), 3,4-dimethyl-1,3-pentadiene (IX), 2-methyl-2,4-hexadiene (XI), and 3-isopropyl-4-methyl-1,3-pentadiene (XIV).     

Direct beta-alkylation of secondary alcohols with primary alcohols catalyzed by a CpIr complex

A new catalytic system for beta-alkylation of secondary alcohols has been developed. In the presence of [CpIrCl(2)](2) (Cp = pentamethylcyclopentadienyl) catalyst and base, the reactions of various secondary alcohols with primary alcohols give beta-alkylated higher alcohols in good to excellent yields without any hydrogen acceptor or hydrogen donor. This reaction proceeds via successive hydrogen-transfer reactions and aldol condensation. [reaction: see text]     

Oxidation of primary and secondary alcohols catalyzed by a pentamethylcyclopentadienyliridium complex

The oxidation of primary and secondary alcohols is carried out in acetone under mild conditions using catalytic amounts of [Cp*IrCl₂]₂ and K₂CO₃. Primary alcohols are converted into the corresponding aldehydes with high selectivity in good yields. Secondary alcohols are readily oxidized to ketones with smaller amounts of the catalyst.     

Kinetic resolution of propargylic alcohols catalyzed by benzotetramisole

[reaction: see text] Kinetic resolution of variously substituted secondary propargylic alcohols catalyzed by benzotetramisole (BTM) proceeds with selectivity factors up to 32, the highest ever achieved with nonenzymatic catalysts for this class of substrates.     

Solvent-free tetrahydropyranylation of alcohols catalyzed by amine methanesulfonates

A comparative study of tetrahydropyranylation of alcohols under various solvents or solvent-free conditions using different amine methanesulfonates as catalysts shows that tetrahydropyranyl ethers of alcohols are obtained under solvent-free conditions in good yields using catalytic amounts of triethylenediamine methanesulfonate, 1,6-hexanediamine methanesulfonate, diethylenetriamine methanesulfonate and pyridine methanesulfonate, respectively. The reaction occurs readily in short times at room temperature catalyzed by these catalysts, especially triethylenediamine methanesulfonate. Some of the major advantages of this procedure are that the catalysts are environmentally friendly, highly effective, and easy to prepare and handle. The reaction is also clean and needs no solvent, and the work-up is very simple.     

Efficient selective oxidation of alcohols to aldehydes catalyzed by a morpholinone nitroxide

Efficient chemoselective oxidation of primary alcohols to the corresponding aldehydes is described. The transformation is promoted by a catalytic morpholinone nitroxide radical catalyst which can be easily synthesized. A broad range of substrates including aromatic and aliphatic primary alcohols are converted with excellent yields under mild conditions. The control experiments reveal that the morpholinone nitroxide can be used as a selective oxidant for primary alcohols in the presence of secondary alcohols.     

Monoalkylation of acetonitrile by primary alcohols catalyzed by iridium complexes

The monoalkylation of acetonitrile by primary alcohols was achieved in a one-pot sequence in the presence of iridium catalysts. A diversity of nitriles has been obtained from aryl- and alkyl-methanols in excellent yield.     

N-Alkylation of carbamates and amides with alcohols catalyzed by a CpIr complex

New atom-economical catalytic systems consisting of [Cp^∗IrCl₂]₂/NaOAc (Cp^∗=pentamethylcyclopentadienyl) for the N-alkylation of carbamates and amides using alcohols as alkylating agents under solvent-free conditions have been developed. For example, the reaction of n-butyl carbamate with benzyl alcohol in the presence of [Cp^∗IrCl₂]₂ (5.0 mol % Ir) and NaOAc (5.0 mol %) at 130 °C under the absence of solvent gives n-butyl N-benzylcarbamate in the yield of 94%. The present catalytic system is applicable to not only carbamates but also amides, and only harmless water is produced as co-product.     

Asymmetric synthesis of propargylic alcohols catalyzed by (−)-MITH

This investigation describes that in the presence of 2.5 mol % of (?)-2-exo-morpholinoisobornane-10-thiol (MITH) 1, catalytic asymmetric alkynylation of aldehydes gives enantioenriched propargylic alcohols with good enantioselectivities.     

Chemoselective trimethylsilylation of alcohols catalyzed by saccharin sulfonic acid

Abstract  Saccharin sulfonic acid was easily prepared by the reaction of saccharin with neat chlorosulfonic acid at room temperature. This reagent is efficiently able to catalyze the chemoselective trimethylsilylation of alcohols with hexamethyldisilazane in the presence of amines and thiols. Graphical abstract        

Chemoselective trimethylsilylation of alcohols catalyzed by saccharin sulfonic acid

Abstract  

Saccharin sulfonic acid was easily prepared by the reaction of saccharin with neat chlorosulfonic acid at room temperature. This reagent is efficiently able to catalyze the chemoselective trimethylsilylation of alcohols with hexamethyldisilazane in the presence of amines and thiols.     

Secondary benzylation with benzyl alcohols catalyzed by a high-valent heterobimetallic Ir-Sn complex

A highly efficient secondary benzylation procedure has been demonstrated using a high-valent heterobimetallic complex [Ir2(COD)2(SnCl3)2(Cl)2(mu-Cl)2] 1 as the catalyst in 1,2-dichloroethane to afford the corresponding benzylated products in moderate to excellent yields. The reaction was performed not only with carbon nucleophiles (arenes and heteroarenes) but also with oxygen (alcohol), nitrogen (amide and sulfonamide), and sulfur (thiol) nucleophiles. Mechanistic investigation showed the intermediacy of the ether in this reaction. An electrophilic mechanism is proposed from Hammett correlation.     

Papain catalyzed estehification of alanine by alcohols and diols

Papain catalyzed esterification of Boc-Ala-OH with various alcohols and diols under biphasic conditions was investigated. Long-chain diols HO(CH₂)nOH gave good yields of esterification up to n=10 whereas the homologous alcohols C_nH_2n+1OH condensed well only for n = 2, 4, 6. Esterification with functionnalized primary alcohols is also described.     

Guerbet reaction of primary alcohols leading to beta-alkylated dimer alcohols catalyzed by iridium complexes

[IrCl(cod)]2 and [Cp*IrCl2]2 complexes catalyzed efficiently the Guerbet reaction of primary alcohols to beta-alkylated dimer alcohols in good yields. For instance, the reaction of 1-butanol in the presence of [Cp*IrCl2]2 (1 mol %), t-BuOK (40 mol %), and 1,7-octadiene (10 mol %) produced 2-ethyl-1-hexanol in 93% yield. Various primary alcohols undergo the Guerbet reaction under the influence of Ir complexes to give the corresponding dimer alcohols in good yields. This method provides an alternative direct route to beta-alkylated primary alcohols which are prepared by aldol condensation of aldehydes followed by hydrogenation.     

Dehydration of alcohols on iron Fischer-Tropsch type catalysts

The dehydration of 1-butanol was studied on iron Fischer-Tropsch type catalysts. Chemical trapping allowed us to propose a mechanism involving hydrogenolysis of the C–O bond with the selective formation of 1-butene.

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1- -. , C–O jqz 1-.

     

Ether formation from allylic alcohols catalyzed by samarium trichloride

The behaviour of various allylic alcohols in the presence of catalytic amounts of SmCl₃ (by heating in 1,2-dichloroethane) has been studied. Diallyl ethers are obtained in many cases in good yields. Mixed allyl alkyl ethers are also prepared if 2–5 equivalents of an aliphatic alcohol is present. The reactions are interpreted as proceeding through a pseudo allylic carbonium intermediate initiated by a preliminary complexation of the allyl hydroxyl to the samarium ion.