Synthesis of benzyl alcohols
The use of bis(methanesulfonyl) peroxide as an oxidant enables a selective synthesis of benzylic alcohols without further oxidation of alcohols to ketones. A proton-coupled electron transfer mechanism (PCET) may account for the difference in reactivity.
L. Tanwar, J. Börgel, T. Ritter, J. Am. Chem. Soc., 2019, 141, 17983-17988.
Diverse alcohols were synthesized by metal-free coupling of diazoalkanes derived from p-toluenesulfonylhydrazones to water under reflux and microwave conditions, in high yields. In addition, this protocol was successfully applied in the synthesis of deuterium-labeled alcohols using deuterium oxide.
Á. García-Muñoz, A. I. Ortega-Arizmendi, M. A. García-Carrillo, E. Díaz, N. Gonzalez-Rivas, E. Cuevas-Yañez, Synthesis, 2012, 44, 2237-2242.
The use of Oxone allows the conversion of various aryl-, heteroaryl-, alkenyl-, and alkyltrifluoroborates into the corresponding oxidized products in excellent yields. This method tolerates a broad range of functional groups, and in secondary alkyl substrates it was demonstrated to be completely stereospecific.
G. A. Molander, L. N. Cavalcanti, J. Org. Chem., 2011, 76, 623-630.
A visible light-induced photocatalysis enables a general and practical decarboxylative hydroxylation of a broad range of carboxylic acids using molecular oxygen as the green oxidant. NaBH4 as additive reduces unstable peroxyl radical intermediates in situ.
S. N. Khan, M. K. Zaman, R. Li, Z. Sun, J. Org. Chem., 2020, 85, 5019-5026.
A photocatalytic direct decarboxylative hydroxylation of carboxylic acids enables the conversion of various readily available carboxylic acids to alcohols in good yields under extremely mild reaction conditions using molecular oxygen as a green oxidant and visible light as a driving force.
H.-T. Song, W. Ding, Q.-Q. Zhou, J. Liu, L.-Q. Lu, W.-J. Xiao, J. Org. Chem., 2016, 81, 7250-7255.
Ubiquitous carboxylic acids can serve as starting materials for a photocatalytic decarboxylative C-O bond formation reaction that provides rapid and facile access to the corresponding acetoxylated products.
S. Senaweera, K. C. Cartwrigt, J. A. Tunge, J. Org. Chem., 2019, 84, 12334-12343.
A formic acid promoted hydration of readily available alkynes followed by an iridium-catalyzed transfer hydrogenation under mild conditions provides alcohols. This transformation is simple, efficient, and can be performed with a variety of alkynes in good yields and with excellent stereoselectivities.
N. Luo, Y. Zhong, J.-T. Liu, L. Ouyang, R. Luo, Synthesis, 2020, 52, 3439-3445.
Two complementary dual catalytic systems enable a highly regioselective reductive hydration of terminal alkynes to yield branched or linear alcohols in very good yield. The method is compatible with terminal, di-, and trisubstituted alkenes. This reductive hydration constitutes a strategic surrogate to alkene oxyfunctionalization and may be of utility in multistep settings.
L. Li, S. B. Herzon, J. Am. Chem. Soc., 2012, 134, 17376-17378.
The neutral gold(I) complex [(IPr)AuCl] is a highly effective catalyst for the regioselective hydration of terminal alkynes, including aromatic alkynes and aliphatic alkynes providing methyl ketones in high yields. Furthermore, optically active alcohols could be obtained in high yields with very good enatioselectivities via one-pot sequential hydration/asymmetric transfer hydrogenation using Cp*RhCl[(R,R)-TsDPEN] as additional catalyst.
F. Li, N. Wang, L. Lu, G. Zhu, J. Org. Chem., 2015, 80, 3538-3546.
In a rhenium-catalyzed oxyalkylation of alkenes, hypervalent iodine(III) reagents derived from widely occurring aliphatic carboxylic acids were not only an oxygenation source but also an alkylation source via decarboxylation. The reaction offers a wide substrate scope, totally regiospecific difunctionalization, mild reaction conditions, and ready availability of both substrates.
Y. Wang, L. Zhang, Y. Yang, P. Zhang, Z. Du, C. Wang, J. Am. Chem. Soc., 2013, 135, 18048-18051.
Various tertiary β-trifluoromethyl alcohols can be synthesized in good yields without transition metal catalysts via a radical trifluoromethylation of alkenes using in situ generated peroxide in NMP under O2 as the radical initiator.
C. Liu, Q. Lu, Z. Huang, J. Zhang, F. Liao, P. Peng, A. Lei, Org. Lett., 2015, 17, 6034-6037.
An esterification of primary benzylic C-H bonds with carboxylic acids using di-tert-butyl peroxide as an oxidant is catalyzed by novel ionic iron(III) complexes containing an imidazolinium cation. The reaction offers a broad generality and tolerates sterically hindered starting materials.
B. Lu, F. Zhu, H.-M. Sun, Q. Shen, Org. Lett., 2017, 19, 1132-1135.
An efficient phosphorylation of C(sp3)-H bonds of readily available methyl arenes with diaryl phosphinic acids proceeds efficiently under transition-metal-free reaction conditions via Bu4NI-catalyzed dehydrogenative coupling to provide valuable organophosphorus compounds.
B. Xiong, G. Wang, C. Zhou, Y. Liu, P. Zhang, K. Tang, J. Org. Chem., 2018, 83, 993-999.
A highly efficient dynamic kinetic resolution (DKR) of secondary alcohols at room temperature was developed. In situ racemization of substrates using a Ru catalyst and lipase-catalyzed acylation provides enantiopure products in high yields in very short reaction times. The use of isopropenyl acetate as the acyl donor makes the purification of the products very easy.
B. Martin-Matute, M. Edin, Krisztian Bogar, J.-E. Baeckvall, Angew. Chem. Int. Ed., 2004, 43, 6535-6539.
Well-defined 16-electron ruthenium complexes bearing an N-heterocyclic carbene ligand are active catalysts in the racemization of chiral alcohols. Mechanistic considerations are presented.
J. Bosson, S. P. Nolan, J. Org. Chem., 2010, 75, 2039-2043.