Categories: C-Cl Bond Formation >
Synthesis of benzyl chlorides
The combination of N-chlorosuccinimide as safe chlorine source with Acr+-Mes as the photocatalyst achieves a benzylic C-H bond chlorination under visible light irradiation. This mild and scalable chlorination method worked effectively for electron-deficient substrates. Furthermore, benzylic chlorides could be converted to benzylic ethers smoothly in one-pot by adding sodium methoxide.
M. Xiang, C. Zhou, X.-L. Yang, B. Chen, C.-H. Tung, L.-Z. Wu, J. Org. Chem., 2020, 85, 9080-9087.
A rapid, selective, and high-yielding chlorination of benzylic alcohols in the presence of 2,4,6-trichloro-1,3,5-triazine and dimethyl sulfoxide takes 10 to 40 minutes. The neutral reaction conditions are compatible with substrates bearing acid-labile functional groups. Both competitive intramolecular and intermolecular reactions for benzyl alcohols in the presence of aliphatic alcohols indicate high selectivity.
L. Sun, G. Peng, H. Niu, Q. Wang, C. Li, Synthesis, 2008, 3919-3924.
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.
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.
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 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.
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.
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.
The use of sodium ion-exchanged montmorillonite enables a practical and efficient chlorination of benzylic and allylic alcohols. The method is characterized by the formation of hydrogen chloride from trimethylsilyl chloride and trace water, the formation of a carbenium ion through the protonation of an alcohol and subsequent dehydration, and the chlorination of the carbenium ion.
M. A. Tandiary, Y. Masui, M. Onaka, Synlett, 2014, 25, 2639-2643.
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.
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.
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.
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.
The use of (dichloroiodo)benzene enables a mild and rapid nucleophilic chlorination of readily available secondary and tertiary alkyl phenyl sulfides. Enantioenriched benzylic sulfides can be converted to their corresponding inverted chlorides with high stereospecificity. The chlorination of sulfa-Michael derived sulfides provides elimination-sensitive β-chloro carbonyl and nitro compounds in good yields.
D. Canestrari, S. Lancianesi, E. Badiola, C. Strinna, H. Ibrahim, M. F. A. Adamo, Org. Lett., 2017, 19, 918-921.
Phthaloyl chloride as reagent and N-formylpyrrolidine as Lewis base catalyst enable a transformation of aldehydes into geminal dichlorides. This simple reaction offers mild reaction conditions, high levels of functional group compatibility, and scalability.
P. H. Huy, Synthesis, 2019, 51, 2474-2483.
A mild and efficient protocol enables the preparation of 1,2-dichloroalkane derivatives from olefins in the presence of NH4Cl and Oxone at room temperature. Various terminal, internal, and cyclic alkenes reacted smoothly to give the corresponding dichlorinated products in good to excellent yields. Internal olefins dichlorinated with moderate to excellent diastereoselectivity.
P. Swamy, M. M. Reddy, M. A. Kumar, M. Naresh, N. Narender, Synthesis, 2014, 46, 251-257.
Aryl aldehydes couple readily with allylmetals to afford haloallylated products in the presence of boron trihalides. The reactions tolerate a variety of functional groups. Simple aqueous workup of haloallylation reactions, followed by treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene, provides a straightforward route to synthetically useful (E)-1,3-dienes.
M. P. Quinn, M.-L. Yao, G. W. Kabalka, Synthesis, 2011, 3815-3820.
A hypervalent iodine reagent-based α-carbonyl dihalogenation of diazoacetate derivatives with either iodobenzene dichloride or iodotoluene difluoride results in gem-dichlorination or gem-difluorination products, respectively. The reaction is catalyzed by either Lewis acid or Lewis base and proceeds rapidly and chemoselectively to the desired gem-difunctionalized products in very good yield.
J. Tao, R. Tran, G. K. Murphy, J. Am. Chem. Soc., 2013, 135, 16312-16315.
The combination of 2-NsNCl2/2-NsNHNa as the nitrogen and chlorine sources and copper(I) triflate as the catalyst enables a regio- and stereoselective aminochlorination of cinnamic esters to provide anti-alkyl 3-chloro-2-(o-nitrobenzenesulfonamido)-3-phenylpropionate derivatives with good yields and stereoselectivity.
G. Li, H.-X. Wei, S. H. Kim, Org. Lett., 2000, 2, 2249-2252.
The regio- and stereoselective aminochlorination of α,β-unsaturated ketones with N,N-dichloro-p-toluenesulfonamide (4-TsNCl2) and CuOTf as catalyst provides an easy access to vicinal haloamino ketones, with excellent regioselectivity and good yields. Aromatic and aliphatic enones give opposite regioselectivity.
D. Chen, C. Timmons, S. Chao, G. Li, Eur. J. Org. Chem., 2004, 3097-3101.