Sodium perborate
Sodium perborate (SPB) is used in the detergent industry as a bleaching agent. The crystalline reagent is available inexpensively as a hydrate with the general formula NaBO3 • n H2O (n: 1-4). Indeed, the compound itself is a dimer:
The reagent offers low toxicity and a long shelf life. SPB is a useful reagent in organic synthesis as a substitute for the unstable, highly concentrated hydrogen peroxide solutions that can pose a significant explosion hazard and are not commercially available.
Sodium perborate is soluble in water and releases hydrogen peroxide, but it is not merely a mixture of hydrogen peroxide and sodium borate. NMR and Raman spectroscopy indicate that in dilute solution, an equilibrium exists that still contains peroxoborate anions. These peroxoborate species are able to deliver the hydroperoxide anion at a lower pH than when H2O2 is used:
A. McKillop, W. R. Sanderson, Tetrahedron, 1995, 51,
6145-6166.
DOI
SPB is activated toward nucleophilic oxidation, and also buffers the reaction medium.
For oxidations of organoboranes, Kabalka notes that H2O2 sometimes requires quite harsh conditions that are incompatible with many functional groups, while SPB offers an interesting mild alternative. He assumes that the mild nature of the oxidant is a result of having borate as a leaving group as compared to hydroxide, which is formed in hydrogen peroxide oxidations:
G. W. Kabalka, T. M. Shoup, N. M. Goudgaon, J. Org. Chem., 1989,
54, 5930-5933.
Mixing sodium perborate with acetic acid generates even more powerful oxidation species. As McKillop states in his review (Tetrahedron, 1995, 51, 6145-6166. DOI), the situation is more complex than a simple conversion of a carboxylic acid to the corresponding peracid might suggest. It is possible that the intermediate peracetoxyboron species might act directly on organic substrates.
For applications in organic synthesis see the following reviews:
J. Muzart, Synthesis, 1995, 1325-1347.
DOI
A. McKillop, W. R. Sanderson, J. Chem. Soc., Perkin Transactions 1,
2000, 471-476.
DOI
Recent Literature
Several primary aromatic amines were converted to their corresponding nitro
compounds in good yields with sodium perborate tetrahydrate (SPB) in micellar
media in the presence of a catalytic amount of tungstophosphoric acid (H3PW·nH2O).
H. Firouzabadi, N. Iranpoor, K. Amani, Green Chemistry,
2001, 3, 131-132.
Sodium perborate in acetic acid is an effective reagent for the oxidation of
aromatic aldehydes to carboxylic acids, iodoarenes to (diacetoxyiodo)arenes,
azines to N-oxides, and various sulphur heterocycles to S,S-dioxides.
Nitriles undergo smooth oxidative hydration to amides when aqueous methanol is
employed as solvent.
A. McKillop, D. Kemp, Tetrahedron, 1989,
45, 3299-3306.
A. McKillop, D. Kemp, Tetrahedron, 1989,
45, 3299-3306.
A. McKillop, D. Kemp, Tetrahedron, 1989,
45, 3299-3306.
A. McKillop, D. Kemp, Tetrahedron, 1989,
45, 3299-3306.
Sodium perborate (SPB), a principal component of washing powders, can be used as
an inexpensive and eco-friendly oxidant in the palladium-catalyzed C-H
acyloxylation of alkenes in excellent regio- and stereochemistry. The reactions
used anhydrides as acyloxy sources. The method enables the conversion of both
terminal and internal alkenes, and allows even benzylic C-H oxidation.
L. T. Pilarski, P. G. Janson , K. J. Szabó, J. Org. Chem., 2011,
76, 1503-1506.
Sodium perborate efficiently oxidizes a wide variety of functionally
substituted organoboranes. The product yields exceed those obtained using
standard oxidation procedures.
G. W. Kabalka, T. M. Shoup, N. M. Goudgaon, J. Org. Chem., 1989,
54, 5930-5933.
A catalytic enantio- and diastereoselective addition of alkyl 1,1-diboron
reagents to aryl and vinyl aldehydes provides 1,2-hydroxyboronates promoted by a
readily available chiral monodentate phosphoramidite-copper complex. Products
contain two contiguous stereogenic centers and are obtained in good yield, good
d.r., and high e.r. The 1,2-hydroxyboronate products can be transformed into
versatile derivatives.
M. V. Joannou, B. S. Moyer, S. J. Meek, J. Am. Chem. Soc., 2015,
137, 6176-6179.
G. W. Kabalka, T. M. Shoup, N. M. Goudgaon, J. Org. Chem., 1989,
54, 5930-5933.
Bidentate Oxazoline-substituted imidazolium salts based on [2.2]paracyclophane
with planar and central chirality can be used as ligand in Cu(I)-catalyzed
asymmetric β-boration of α,β-unsaturated esters, giving the desired products in
high enantioselectivities and yields.
Z. Niu, J. Chen, Z. Chen, M. Ma, C. Song, Y. Ma, J. Org. Chem.,
2015,
80, 602-608.
A Rh-catalyzed hydroboration of α, β-unsaturated carbonyl compounds with
pinacolborane proceeds with high levels of regio-, diastereo-, and
enantioselectivities to provide products with two vicinal stereocenters. Through
the appropriate choice of substrate geometry (E or Z) and ligand
enantiomer, all possible diastereoisomers are readily accessible.
T.-T. Gao, W.-W. Zhang, X. Sun, H.-X. Lu, B.-J. Li, J. Am. Chem. Soc.,
2019,
141, 4670-4677.
A transition-metal-free coupling of aldehydes and ketones with geminal bis(boron)
building blocks provides homologated carbonyl compounds upon oxidation.
Aldehydes with an enolizable stereogenic center undergo this reaction with
complete retention of stereochemistry.
T. C. Stephens, G. Pattison, Org. Lett.,
2017, 19, 3498-3501.
A copper(I)-catalyzed asymmetric borylative propargylation of simple ketones
offers broad substrate scope, good tolerance of functional groups, high
diastereo- and enantioselectivities, and reaction robustness. The borylative
product can also serve as a cross-coupling partner in Pd-catalyzed
Suzuki-Miyaura reactions.
X.-C. Gan, L. Yin, Org. Lett., 2019, 21,
931-936.
Hydroboration of 1-alkynyl-1-boronate esters and in situ transmetalation
furnishes 1-alkenyl-1,1-borozinc heterobimetallic intermediates. Reaction with
aldehydes and in situ cyclopropanation generates B(pin) substituted cyclopropyl
carbinols with excellent diastereoselectivities. Oxidation provides
trisubstituted α-hydroxycyclopropyl carbinols, that allow access to both cis-
and trans-2,3-disubstituted cyclobutanones via a facile pinacol-type
rearrangement.
M. M. Hussain, H. Li, N. Hussain, M. Ureña, P. J. Carroll, P. J. Walsh, J. Am. Chem. Soc., 2009,
131, 6516-6524.
A convenient oxidation of oximes to nitro compounds uses sodium perborate in
glacial acetic acid as oxidizing agent.
G. A. Olah, P. Ramaiah, C.-S. Lee, G. K. Surya Prakash, Synlett,
1992, 337-339.
A Bi(V) compound catalyzes an oxidation of hydrazones into diazo compounds in
the presence NaBO3·H2O as the terminal oxidant. Ph3Bi(OAc)2
as catalyst is in situ generated from BiPh3 and AcOH. The reaction
was applied for the synthesis of diazocarbonyls and 2,2,2-trifluoromethyl
diazoalkanes in very good yields.
N. Tanbouza, L. Caron, A. Khoshoei, T. Ollevier, Org. Lett.,
2022, 24, 2675-2678.