Categories: C-Cl Bond Formation >
Synthesis of alkyl chlorides
A practical nucleophilic substitution of alcohols furnishes alkyl chlorides, bromides, and iodides under stereochemical inversion in the presence of diethylcyclopropenone as a simple Lewis base organocatalyst and benzoyl chloride as a reagent. Moreover, acetyl chloride has been used as a stoichiometric promotor in an invertive SN-type transformation for the first time.
T. Stach, J. Dräger, P. H. Huy, Org. Lett., 2018, 20, 2980-2983.
Substoichiometric amounts of thiourea additives mediate the halogenation of alcohols under mild conditions. In the the absence of thiourea, oxidation of the alcohol is observed, whereas the substrate can be recovered when excess thiourea is used. Both bromination and chlorination were highly efficient for primary, secondary, tertiary, and benzyl alcohols and tolerate a broad range of functional groups.
A. R. Mohite, R. S. Phatake, P. Dubey, M. Agbaria, A. I. Shames, N. G. Lemcoff, O. Reany, J. Org. Chem., 2020, 85, 12901-12911.
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.
In a catalytic system for the chlorination of alcohols under Appel conditions, benzotrichloride is used as a cheap and readily available chlorinating agent in combination with trioctylphosphane as the catalyst and phenylsilane as the terminal reductant under solvent-free conditions. In total, 27 different primary, secondary, and tertiary alkyl chlorides were synthesized in good yields.
L. Longwitz, S. Jopp, T. Werner, J. Org. Chem., 2019, 84, 7863-7870.
The combination of Ph3P and easily available 1,2-dihaloethanes (XCH2CH2X; X = Cl, Br, or I), was very effective for a mild deoxygenative halogenation of alcohols and aldehydes. The use of (EtO)3P instead of Ph3P enables a convenient purification process, as the byproduct (EtO)3P═O could be removed by aqueous washing. A dehydroxy-fluorination proceeds well in the presence of ICH2CH2I and CsF as fluoride source in DMF.
J. Chen, J.-H. Lin, J.-C. Xiao, Org. Lett., 2018, 20, 3061-3064.
The use of α,α-dichlorodiphenylmethane as chlorinating agent and FeCl3 as the catalyst enables a chlorination of alcohols and carboxylic acids to their corresponding alkyl and acyl chlorides in high yields under mild conditions. In the presence of LiBr or LiI, the respective alkyl bromides and iodides can be generated.
C.-H. Lee, S.-M. Lee, B.-H. Min, D.-S. Kim, C.-H. Jun, Org. Lett., 2018, 20, 2468-2471.
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.
The combination of methanesulfonic acid and inorganic halide salts (CaCl2, LiBr, LiI) mediates hydrochlorinations, hydrobrominations, and hydroiodinations of unactivated alkenes in acetic acid. This approach uses readily available and inexpensive reagents to provide alkyl halides in very good yields. An example of deuteriochlorination using deuterated acetic acid as solvent is also demonstrated.
X. Bertrand, P. Paquin, L. Chabaud, J.-F. Paquin, Synthesis, 2022, 54, 1413-1421.
A silver-catalyzed chlorination of benzylic, tertiary, and secondary C(sp3)-H bonds proceeded with as low as 0.2 mol % catalyst loading at room temperature under air atmosphere with synthetically useful functional group compatibility.
J. Ozawa, M. Kanai, Org. Lett., 2017, 19, 1430-1433.
SnCl4 and TiCl4 as Lewis acids and chloride nucleophiles enable selective and regiodivergent openings of unsymmetrical phenonium ions at either the substituted internal position (SnCl4) or unsubstituted terminal position (TiCl4). These reactions are highly selective, stereospecific, operationally simple, and proceed in good to excellent yields.
S. Xu, H. M. Holst, S. B. McGuire, N. J. Race, J. Am. Chem. Soc., 2020, 142, 8090-8096.
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.
A highly regioselective chlorothiolation of alkenes with sulfonyl chlorides is compatible with a variety of functional groups and can be scaled up to the gram scale. The employment of readily available reactants and mild reaction conditions makes this process very practical.
J. Wei, S. Liang, L. Jiang, Y. Mumtaz, Y.-b. Yi, J. Org. Chem., 2020, 85, 977-984.
A sequential installation of a carbenoid and a hydride into a carbonyl provides halomethyl alkyl derivatives with uniformly high yields and chemocontrol. The tactic is flexible and is not limited to carbenoids. Also, diverse carbanion-like species can act as nucleophiles.
M. Miele, A. Citarella, T. Langer, E. Urban, M. Zehl, W. Holzer, L. Ielo, V. Pace, Org. Lett., 2020, 22, 7629-7634.