A Simple Procedure for the Oxidation of Alcohols Using [Bis(acetoxy)iodo]benzene and a Catalytic Amount of Bromide Ions in Ethyl Acetate

Abstract

OH R 2 R 1 EtOAc, r.t., 24 h O R 2 R 1 primary and secondary benzylic alcohols secondary aliphatic alcohols PhI(OAc) 2 (1.1 equiv) Br -(5 or 20 mol%) TEMPO (1 mol%) OH R 2 R 1 primary aliphatic and secondary allylic alcohols conv. >90% 19 examples CH 2 Cl 2 or EtOAc r.t., 2 h PhI(OAc) 2 (1.1 equiv) KBr (20 mol%) without TEMPO Abstract Primary and secondary benzylic alcohols and secondary aliphatic alcohols were oxidized to the corresponding aldehydes and ketones by using [bis(acetoxy)iodo]benzene (BAIB) and a catalytic amount of bromide ions, from tetrabutylammonium bromide or KBr, in ethyl acetate. The catalytic role of the bromide ions was also highlighted in the oxidation of primary aliphatic alcohols and secondary allylic alcohols carried out in the presence of 1 mol% TEMPO.Oxidation of alcohols is a process that has interested chemists for a very long time. The usefulness of the reaction is well known and a large number of oxidation methods is now available. Several methods are based on the use of a stoichiometric amount of metal-based oxidants such as Collins reagent, pyridinium dichromate or chlorochromate. 1 Methods involving the use of a catalytic amount of metalbased oxidants are also available, such as tetrapropylammonium perruthenate in the presence of an excess of Nmethylmorpholine oxide. 2 Recent demand for green oxidation processes has encouraged the development of cleaner and safer oxidation reactions. The use of soluble metalbased oxidants or catalysts can be avoided by using supported metal catalysts. 3 On the other hand, the use of metal-free catalysts for selective oxidations of organic substrates is very appealing, and several organic oxidants can be used, such as activated dimethyl sulfoxide (DMSO) 4 or catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) in the presence of NaOCl. 5 TEMPO can also be used with stoichiometric amounts of inexpensive, safe, and easy to handle oxidants such as [bis(acetoxy)iodo]benzene (BAIB), 6 trichloro isocyanuric acid, 7 Oxone, 8 or iodine. 9 Among them, hypervalent iodine compounds such as BAIB have been used successfully. 10 Pentavalent iodine reagents such as Dess-Martin periodinane 11 and o-iodoxybenzoic acid 12 are mild and efficient oxidizing agents that allow carbonyl compounds to be obtained from alcohols with high yields in organic solvents such as CH 2 Cl 2 , DMSO, and acetone. However, iodine(V) reagents cannot be stored for a long time. In place of iodine(V) reagents, readily available and relatively stable iodine(III) reagents can be used. The group of Kita has described several examples of oxidation of alcohols by using iodine(III) reagents. They reported the use of iodosobenzene (PhIO) with KBr, in water under neutral conditions 13 as well as the use of polymer-supported (diacetoxyiodo)benzene (PSDIB). 14 Under these conditions, acids, ketones, and lactones were obtained. Instead of KBr, the same authors employed Et 4 N + Br -in water. Under the latter conditions, several secondary alcohols were easily converted into the correspo...

Dihydrolevoglucosenone (Cyrene™), a new possibility of an environmentally compatible solvent in synthetic organic electrochemistry

“…The starting materials (1) were synthesized following synthetic procedures reported in the literature. 30,31 Absolute ethanol was purchased from Tecsiquim and was used without prior treatment. Dihydrolevoglucosenone (DLG or Cyrene™) was purchased from Sigma-Aldrich and was used without prior treatment for electrosynthesis.…”

Applications of Phenyliodine(III)diacetate in C−H Functionalization and Hetero‐Hetero Bond Formations: A Septennial Update

“…PIDA is also used in a variety of medical, industrial, and human and animal nutrition products, including antiseptics and disinfectants, pharmaceutical intermediates, and polarising films for liquid crystal displays [LCD]. In the past three decades, a number of reviews, books, and book chapters have been written; some are comprehensive, while the majority attention on certain facets of polyvalent organoiodine chemistry focusing on PIDA [27–78] . Zhdankin and Yoshimura evaluated the literature from publications through the summer of 2015 in order to examine improvements in the synthetic uses of hypervalent iodine compounds [7] .…”

Experimental and theoretical study of α-acetoxylation of ketones by (diacetoxy)iodobenzene

“…Hypervalent iodine(III) compounds function as effective reagents for synthesizing various compounds, such as a-hydroxy carbonyl, 1-3 a-tosylate carbonyl, 4,5 and a-acetoxy carbonyl, 3,[6][7][8][9] as well as in alcohol oxidations, [10][11][12] rearrangements, 13,14 and other reactions. [15][16][17][18] Several organic chemists have studied these reactions; nevertheless, the a-acetoxylation of ketones using diacetoxyiodobenzene (PIDA) is a reaction with many protocols and mechanistic studies.…”