Sodium Hypochlorite, Bleach, NaOCl
Sodium hypochlorite is an inexpensive, strong oxidizing agent, that is used as disinfectant and bleaching agent. It is unstable as a solid, but solutions of up to 40% are commercially available that contain NaOH and NaCl as byproducts of the preparation:
2 NaOH + Cl2 → NaCl + NaOCl + H2O
Hypochlorite solutions liberate toxic gases such as chlorine when acidified or heated. The reaction with ammonia or with substances that can generate ammonia can produce chloramines which are also toxic and have explosive potential.
TEMPO-derived reagents tagged with multiple perfluoroalkyl chains and triazole moieties promote the oxidation of alcohols to aldehydes in organic solvent/water mixtures with reaction rates comparable to homogeneous TEMPO reagents, but can be easily recovered by liquid/emulsion filtration.
A. Gheorghe, T. Chinnusamy, E. Cuevas-Yañez, P. Hilgers, O. Reiser, Org. Lett., 2008, 10, 4171-4174.
Sodium hypochlorite pentahydrate crystals with very low NaOH and NaCl contents oxidize primary and secondary alcohols to the corresponding aldehydes and ketones in the presence of TEMPO/Bu4NHSO4 without pH adjustment. This new oxidation method is also applicable to sterically hindered secondary alcohols.
T. Okada, T. Asawa, Y. Sugiyama, M. Kirihara, T. Iwai, Y. Kimura, Synlett, 2014, 25, 596-598.
A stable nitroxyl radical class of catalysts, 2-azaadamantane N-oxyl (AZADO) and 1-Me-AZADO, exhibit superior catalytic proficiency to TEMPO, converting various sterically hindered alcohols to the corresponding carbonyl compounds in excellent yields.
M. Shibuya, M. Tomizawa, I. Suzuki, Y. Iwabuchi, J. Am. Chem. Soc., 2006, 128, 8412-8413.
The use of NaClO/TEMPO/Co(OAc)2 enabled a benzylic oxidation of alkyl arenes to yield various aromatic aldehydes and ketones in very good yields. The reaction reactivity, selectivity, and scope of the reaction were investigated.
C. Jin, L. Zhang, W. Su, Synlett, 2011, 1435-1438.
An efficient and practical method enables the synthesis of unsymmetric benzils from readily available β-ketoaldehydes via oxidation by sodium hypochlorite, decarboxylation, and chlorination with Cl2 generated from sodium hypochlorite. Various unsymmetric 1,2-diaryldiketones bearing functional groups have been obtained in very good yields under mild reaction conditions.
L. Ruan, M. Shi, N. Li, X. Ding, F. Yang, J. Tang, Org. Lett., 2014, 16, 733-735.
A general procedure for the osmium-catalyzed dihydroxylation of various terminal and internal olefins using bleach as cheap oxidant yields the corresponding cis-1,2-diols in the presence of dihydroquinine or dihydroquinidine derivatives (Sharpless ligands) with good to excellent chemo- and enantioselectivities under optimized pH conditions.
G. M. Mehltretter, S. Bhor, M. Klawonn, C. Döbler, U. Sundermeier, M. Eckert, H.-C. Militzer, M. Beller, Synthesis, 2003, 295-301.
Promising, dual-functioning chiral catalysts for the highly enantioselective epoxidation of α,β-unsaturated ketones gave epoxy chalcones in excelllent yield and high enantioselectivity using 13% NaOCl as oxidizing agent in toluene under mild phase-transfer conditions.
T. Ooi, D. Ohara, M. Tamura, K. Maruoka, J. Am. Chem. Soc., 2004, 126, 6844-6845.
Readily available Mn(III) complexes catalyze alkene epoxidation by bleach in good yields. A highly enantioselective epoxidation catalyst was developed through a logical sequence of ligand modifications.
E. N. Jacobsen, W. Zhang, A. R. Muci, J. R. Ecker, L. Deng, J. Am. Chem. Soc., 1991, 113, 7063-7064.
A catalyst-free oxidation of sulfides with sodium hypochlorite pentahydrate crystals in an aqueous acetonitrile solution selectively produces the corresponding sulfoxides in high yields in an environmentally benign fashion.
T. Okada, H. Matsumuro, S. Kitagawa, T. Iwai, K. Yamazaki, Y. Kinoshita, Y. Kimura, M. Kirihara, Synlett, 2015, 26, 2547-2552.
A clean and economic synthesis of alkanesulfonyl chlorides via bleach-mediated oxidative chlorosulfonation of S-alkyl isothiourea salts is simple, environment- and worker-friendly. The procedure uses readily accessible reagents, offers safe operations and easy purification without chromatography, and affords high yields.
Z. Yang, B. Zhou, J. Xu, Synthesis, 2014, 46, 225-229.
A Pd-catalyzed coupling of aryl iodides and the sulfur dioxide surrogate DABSO provides aryl ammonium sulfinates, that can be transformed in a one-pot process to various functionalized sulfonamides by simple treatment with an aqueous solution of the relevant amine and sodium hypochlorite (bleach). A broad range of amines, including anilines, and amino acid derivatives can be used.
E. F. Flegeau, J. M. Harrison, M. C. Willis, Synlett, 2016, 27, 101-105.
Sodium hypochlorite pentahydrate (NaClO·5H2O) enables an inexpensive, safe, and rapid oxidation of iodoarenes to provide synthetically useful (diacetoxyiodo)arenes as precursors of various organo-λ3-iodanes such as hydroxyl(tosyloxy)iodobenzene, iodosylbenzene, iodonium ylide, etc.
A. Watanabe, K. Miyamoto, T. Okada, T. Asawa, M. Uchiyama, J. Org. Chem., 2018, 83, 14262-14268.
The use of cheap and innocuous reagents, such as NaClO2, NaOCl, and catalytic amounts of TEMPO enables an environmentally friendly C(sp3)-H oxidation of piperazines and morpholines to 2,3-diketopiperazines and 3-morpholinones, respectively. In addition, by using a stoichiometric amount of TEMPO, 2-alkoxyamino-3-morpholinones can be prepared from morpholine derivatives.
D. Chamorro-Arenas, U. Osorio-Nieto, L. Quintero, L. Hernández-García, F. Sartillo-Piscil, J. Org. Chem., 2018, 83, 15333-15346.
A divergent and regioselective synthesis of either 3-substituted benzisoxazoles or 2-substituted benzoxazoles from readily accessible ortho-hydroxyaryl N-H ketimines proceeds in two distinct pathways through a common N-Cl imine intermediate: (a) N-O bond formation to form benzisoxazole under anhydrous conditions and (b) NaOCl mediated Beckmann-type rearrangement to form benzoxazole, respectively.
C.-y Chen, T. Andreani, H. Li, Org. Lett., 2011, 13, 6300-6303.
Bleach oxidizes trimethylsilyl cyanide to generate an electrophilic cyanating reagent that readily reacts with an amine nucleophile. This oxidative N-cyanation reaction enables the synthesis of disubstituted cyanamides without using highly toxic cyanogen halides.
C. Zhu, J.-B. Xia, C. Chen, Org. Lett., 2014, 16, 247-249.