Categories: C-Cl Bond Formation >
Synthesis of alkyl chlorides
The use of chloro tropylium chloride enables a rapid generation of alkyl halides and acyl chlorides from alcohols and carboxylic acids under very mild reaction conditions via aromatic tropylium cation activation. This reactions demonstrate the synthetic potential of tropylium cations in promoting chemical transformations.
T. V. Nguyen, A. Bekensir, Org. Lett., 2014, 16, 1720-1723.
The use of a tetraethylammonium halide in the presences of [Et2NSF2]BF4 (XtalFluor-E) enables efficient chlorination and bromination reactions of a wide range of alcohols. Iodination reactions are also possible albeit in lower yields. As opposed to Appel reactions, water-soluble side products are generated, that facilitate work-up.
M.-F. Pouliot, O. Mahé, J.-D. Hamel, J. Desroches, J.-F. Paquin, Org. Lett., 2012, 14, 5428-5431.
Activation of primary aliphatic alcohols with triphosgene and triethylamine mixtures afforded either alkyl chloride or diethylcarbamate products driven by sterics. The reaction conditions were unexceptionally mild and readily tolerated by a wide range of sensitive functionalities.
C. E. Ayala, A. Villalpando, A. L. Nguyen, G. T. McCandless, R. Kartika, Org. Lett., 2012, 14, 3676-3679.
Unactivated secondary and α-branched primary aliphatic alcohols have been transformed into their corresponding alkyl chlorides in high yields in the presence of triphosgene and pyridine in dichloromethane at reflux. These mild chlorination conditions are stereospecific and well tolerated by numerous sensitive functionalities. Furthermore, no nuisance waste products are generated in the course of the reactions.
A. Villalpando, C. E. Ayala, C. B. Watson, R. Kartika, J. Org. Chem., 2013, 78, 3989-3996.
Ionic liquids [bmim][X] (X = Cl, Br, I, OAc, SCN) are highly efficient reagents for nucleophilic substitution reactions of sulfonate esters derived from primary and secondary alcohols. The newly developed protocol is very environmentally attractive because the reactions use stoichiometric amounts of ionic liquids as sole reagents without additional solvents and activating reagents. Moreover, these ionic liquids can be readily recycled.
Y. Liu, Y. Xu, S. H. Jung, J. Chae, Synlett, 2012, 23, 2663-2666.
Nucleophilic fluorination using CsF or alkali metal fluorides was completed in short reaction time in the presence of [bmim][BF4] affording the desired products without any byproducts. Facile nucleophilic substitutions such as halogenations, acetoxylation, nitrilation, and alkoxylations in the presence of ionic liquids provided the desired products in good yields.
D. W. Kim, C. E. Song, D. Y. Chi, J. Org. Chem., 2003, 68, 4281-4285.
A user-friendly exchange reaction enables an efficient preparation of alkyl chlorides in excellent yields from secondary alkyl sulfonates by using benzyltributylammonium chloride in acetone. The reaction tolerates functionalized, base-sensitive and hindered secondary alkyl sulfonates.
G. Cahiez, N. Lefèvre, M. Poizat, A. Moyeux, Synthesis, 2013, 45, 231-236.
The preparation of alkenyl halides of any length from inexpensive starting reagents is reported. Standard organic transformations were used to prepare straight-chain α-olefin halides in excellent overall yields with no detectable olefin isomerization and full recovery of any unreacted starting material.
T. W. Baughman, J. C. Sworen, K. B. Wagener, Tetrahedron, 2004, 60, 10943-10948.
The reaction of alcohols and β-amino alcohols with 2,4,6-trichloro[1,3,5]triazine and N,N-dimethylformamide in methylene chloride at room temperature gave the corresponding chlorides, and with NaBr gave the corresponding bromides in high yields.
L. de Luca, G. Giacomelli, A. Porcheddu, Org. Lett., 2002, 4, 553-555.
The counteranions of CuCl2 functioned as a chloride source in a reductive chlorination of carboxylic acids in the presence of a gallium(III) catalyst and a hydrosiloxane.
N. Sakai, T. Nakajima, S. Yoneda, T. Konakahara, Y. Ogiwara, J. Org. Chem., 2014, 79, 10619-10623.
An efficient, catalytic Hunsdiecker reaction of aliphatic carboxylic acids affords the corresponding chlorodecarboxylation products in high yields under mild conditions in the presence of t-butyl hypochlorite and Ag(Phen)2OTf as catalyst. The reaction exhibits remarkable functional group compatibility.
Z. Wang, L. Zhu, F. Yin, Z. Su, Z. Li, C. Li, J. Am. Chem. Soc., 2012, 134, 4258-4263.
A mild and metal-free method for the chlorodeboronation of organotrifluoroborates using trichloroisocyanuric acid (TCICA) converts aryl-, heteroaryl-, alkenyl-, alkynyl-, and alkyltrifluoroborates into the corresponding chlorinated products in good yields. This method tolerates a broad range of functional groups.
G. A. Molander, L. N. Cavalcanti, J. Org. Chem., 2011, 76, 7195-7203.
An efficient InCl3-catalyzed reaction of secondary, tertiary and benzylic alcohols with chlorodimethylsilane in the presence of benzil gave the corresponding organic chlorides under mild conditions. In the absence of benzil, the reducing products through dehydroxyhydration were obtained.
M. Yasuda, S. Yamasaki, Y. Onishi, A. Baba, J. Am. Chem. Soc., 2004, 126, 7186-7187.
An indium(III) hydroxide-catalyzed reaction of carbonyls and chlorodimethylsilane afforded the corresponding deoxygenative chlorination products. Ester, nitro, cyano, or halogen groups were not affected during the reaction course. Typical Lewis acids such as TiCl4, AlCl3, and BF3·OEt2 showed no catalytic activity. The reaction mechanism is discussed.
Y. Onishi, D. Ogawa, M. Yasuda, A. Baba, J. Am. Chem. Soc., 2002, 124, 13690-13691.
Group 5 and 6 metal chlorides were found as very efficient catalysts for acylative cleavage of ethers. Compared with conventional Lewis acid catalysts, group 5 and 6 metal chlorides showed better results in the catalytic C-O bond cleavage.
Q. Guo, T. Miyaji, R. Hara, B. Shen, T. Takahashi, Tetrahedron, 2002, 58, 7327-7334.
A silver-catalyzed ring-opening chlorination of cycloalkanols enables a regioselective, efficient, and pratical approach to carbonyl-containing alkyl chlorides with good yields under mild conditions. The chlorinated products are readily transformed into other useful synthetic intermediates and drugs.
F.-Q. Huang, J. Xie, J.-Guo Sun, Y.-W. Wang, X. Dong, L-W. Qi, B. Zhang, Org. Lett., 2016, 18, 684-687.
Halofluorination of alkenes in the presence of trihaloisocyanuric acids and HF•pyridine results in the formation of vicinal halofluoroalkanes in good yields. The reaction is regioselective leading to Markovnikov-oriented products and the halofluorinated adducts follow anti-addition in the case of cyclohexene and 1-methylcyclohexene.
L. T. C. Crespo, R. da S. Ribeiro, M. S. S. de Mattos, P. M. Esteves, Synthesis, 2010, 2379-2382.
In a photoredox vicinal chlorotrifluoromethylation in the presence of Ru(Phen)3Cl2 as catalyst, various terminal and internal alkenes can be transformed to their vicinal chlorotrifluoromethylated derivatives using CF3SO2Cl as a source for CF3 radicals and chloride ions.
S. H. Oh, Y. R. Malpani, N. Ha, Y.-S. Jung, S. B. Han, Org. Lett., 2014, 16, 1310-1313.