Propargyl alcohol silver

Li and coworkers have reported a novel silver-catalyzed, three-component coupling of an aldehyde, an amine, and an alkyne, and the first example of a direct addition of a silver acetylide to an aldehyde to produce propargylic alcohols (Scheme 1.41).103-105 Treatment of an aldehyde with a silver halide and secondary amine gave propargylic amines in good yields in organic solvent, water, or ionic liquids. The proposed mechanism suggests addition of a silver acetylide to the iminium ion formed in situ. 

An extension of the original methodology has seen the synthesis of propargylic alcohols in moderate to good yields from silver acetylides via zirconium acetylides (Scheme 1.45).108... 

The first nonambiguous report of rearrangement of esters derived from propargyl alcohols promoted by silver salts was due to Saucy and coworkers at Hoffmann-La Roche.50 Their observations on the transformation of acetate derived from... 

Although acyloxy, phosphatyloxy, and tosyl allenones were obtained from the corresponding propargyl alcohol derivatives via silver catalysis through an overall process that resembled [3,3]-sigmatropic rearrangement (see Sections 3.41 and 3.43), the mechanism was not fully proved and is still in question. 

Silver acetylides also reacted with epoxides yielding propargylic alcohols.27 As for related alkylations with silver acetylides (see Section 10.6.1), this reaction required zirconocene dichloride and catalytic amount of silver triflate. This method proved useful for both electron-rich and electron-deficient alkynes and compatible with various acid- and base-sensitive functional groups (Table 10.2). 

Rearrangement of propargylic alcohols to enals or enonesIn the presence of a carboxylic acid (generally 7 equiv. of p-toluic acid or crotonic acid), propargylic alcohols are rearranged to enals or enones by Ti(OBu)4 in combination with CuCl, both in about 0.02 mole %. Silver trifluoroacetate can replace CuCl, but yields are lower. The acid is not mandatory, but can increase the rate and yield. 

A range of thiazoles with various combinations of Ri, R2, and R3 substituents was synthesized using this method. The silver-catalyzed cycloaddition of propargylic alcohol with thioamide was proposed to proceed through the intermediacy of a propargylic cation or the corresponding allenyl cation and its subsequent reaction with the nucleophilic sulfiir of thioamide, followed by a 5-exo-dig attack by nitrogen. 

A mild and direct process for C-C bond formation from propargylic alcohols and olefins has been developed in the presence of a silver catalyst (Ji et al. 2009) (Scheme 11.1). In this reaction, trace amounts of water were necessary and allene alcohols and 1,3-dienes were obtained selectively. 

Oleic acid Oxalic acid Pentane Petroleum ether Phosphoric acid, cone. Propyl alcohol Potassium aluminum alum Potassium bichromate Potassium bromate Potassium bromide Potassium chloride Potassium nitrate Potassium perchiorata Potassium permanganate Potassium persulphate Potassium sulphate Propargyl alcohol Propionic acid (20%) Silicone oil Silver nitrate Sodium bicarbonate Sodium bisulphate Sodium bisulphite Sodium carbonate Sodium chlorate Sodium chloride Sodium hypochlorite Sodium sulphate Stannous chloride Sulphur... 

The selective formation of Z-isomer of cyclic carbonate 9 from alcohol 8 was achieved using supercritical CO2 and 7-methyl-l,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) catalysis (Scheme 5) [20]. It should be noted that similar incorporation of CO2 and formation of substituted cyclic carbonates was also successfully carried out with variety of propargylic alcohols in toluene at room temperature and 1 MPa pressure using catalysis by silver acetate and l,8-diazabicycloundec-7-ene (DBU) [21]. 

W. Yamada, Y. Sugawara, H.M. Cheng, T. Ikeno, T. Yamada, Silver-catalyzed incorporation of carbon dioxide into propargylic alcohols, Eur. J. Qrg. Chem. (2007) 2604-2607. 

H.-F. Jiang, J.-W. Zhao, Silver-catalyzed activation of internal propargylic alcohols in supercritical carbon dioxide efficient and eco-friendly synthesis of 4-alkylidene-l,3-oxazoHdin-2-ones, Tetrahedron Lett. 50 (2009) 60-62. 

X. Tang, C. Qi, H. He, H. Jiang, Y. Ren, G. Yuan, Polystyrene-supported N-heterocyclic carbene-silver complexes as robust and efficient catalysts for the reaction of carbon dioxide and propargylic alcohols, Adv. Synth. Catal. 355 (2013) 2019-2028. 

Propargyl cations may also be generated by heterolytic fission of the C—X bond of allenyl derivatives (178). Early attempts to solvolyse chloride 178 (R = H R = Me) in alcoholic solution, even in the presence of silver nitrate, did not furnish reliable conclusions concerning the possibility of unimolecular solvolysis through the propargyl cation (Pudovik, 1951 Hennion and Maloney, 1951). The apparently slow... 

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