Categories: C-C Bond Formation > Oxygen-containing molecules > Carbonyl compounds >
Synthesis of acyloins (α-hydroxy carbonyl compounds)
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Recent Literature
Lanthanum tricyanide efficiently catalyzes a benzoin-type coupling between acyl
silanes and ketones. Good yields are obtained over a broad substrate scope
encompassing aryl, alkyl, and sterically hindered ketones.
J. C. Tarr, J. S. Johnson, Org. Lett., 2009,
11, 3870-3873.
Operationally simple cyanide-catalyzed silyl benzoin reactions afforded
unsymmetrical aryl-, heteroaryl-, and alkyl-substituted silyl ether protected
benzoin adducts with complete regiocontrol.
X. Linghu, J. S. Johnson, Angew. Chem. Int. Ed., 2003, 42,
2534-2536.
A hydrogen bond donating substituent to improve enantiocontrol together with an
acidifying pentafluorophenyl substituent to enhance catalyst efficiency results
in a triazolium ion precatalyst that promotes the asymmetric benzoin
condensation with excellent efficiency and unprecedented enantioselectivity.
L. Baragwanath, C. A. Rose, K. Zeitler, S. J. Connon, J. Org. Chem., 2009,
74, 9214-9217.
The development of a triazolium salt as an efficient precatalyst for the
asymmetric benzoin condensation is described. The high asymmetric inductions
in benzoin condensations are a result of the conformational rigidity of the
bicyclic nucleophilic carbene catalyst and the shielding of the Breslow
intermediate by the sterically demanding tert-butyl group.
D. Enders, U. Kallfass, Angew. Chem. Int. Ed., 2002, 41,
1743-1745.
The appropriate choice of N-heterocyclic carbene catalysts enables an
unprecedented high level of regioselectivities in the intermolecular crossed
acyloin condensations of various aromatic aldehydes with acetaldehyde.
M. Y. Jin, S. M. Kim, H. Han, D. H. Ryu, J. W. Yang, Org. Lett., 2011,
13, 880-883.
An operationally simple and mild visible-light, single-electron-transfer (SET),
photoredox cross-coupling enables the synthesis of α-alkoxyketones in high
yields from various aliphatic and aromatic acyl chlorides and structurally
diverse potassium alkoxymethyltrifluoroborates. The bond connection is unique to
both alkylboron chemistry and photoredox/Ni catalysis.
J. Amani, E. Sodagar, G. A. Molander, Org. Lett., 2016, 18,
732-735.
A one-pot method allows the synthesis of α-siloxy-Weinreb amides from aldehydes
using N,O-dimethylhydroxylamine and a masked acyl cyanide reagent bearing
a tert-butyldimethylsilyl group. The TBS group avoids the competitive
reaction toward N-methoxy-N-methyl-2-amino-1-siloxymalononitrile.
H. Nemoto, R. Ma, H. Moriguchi, T. Kawamura, M. Kamiya, M. Shibuya, J. Org. Chem., 2007,
72, 9850-9853.
β-Silyloxy-α-keto esters are prepared through a cyanide-catalyzed benzoin-type
reaction with silyl glyoxylates and aldehydes. A subsequent dynamic kinetic
resolution provides enantioenriched orthogonally protected alcohols, that can be
converted to the corresponding β-silyloxy-α-amino esters.
K. M. Steward, J. S. Johnson, Org. Lett., 2010,
12, 2864-2867.
Visible-light-induced singlet nucleophilic carbene intermediates can be
trapped by fluorinated ketones via 1,2-carbonyl addition to afford benzoin-type
products. This efficient, user-friendly, and scalable process provides
fluorinated tertiary alcohol derivatives without exogenous catalysts or
additives.
D. L. Priebbenow, R. L. Pilkington, K. N. Hearn, A. Polyzos, Org. Lett., 2021, 23,
2783-2789.
An enantioselective intramolecular crossed-benzoin reaction catalyzed by
novel chiral N-heterocyclic carbenes has been developed. A tetracyclic
trazolium salt catalyzes the cyclization with generation of a quartenary
stereocenter in high yields and excellent enantomeric excess.
D. Enders, O. Niemeier, T. Balensiefer, Angew. Chem. Int. Ed.,
2006,
45, 1463-1467.
While 3,4;5,6-di-O-isopropylidene-N-phthaloyl-D-glucosamine
propane-1,3-diyl dithioacetal underwent fast β-elimination, the corresponding
N-acetyl derivative was easily deprotonated with butyllithium to form the
dilithiated intermediate. Stoichiometry and temperature were crucial factors for
selective C-C coupling with various electrophiles.
Y.-L. Chen, R. Leguijt, H. Redlich, R. Fröhlich,
Synthesis, 2006, 4212-4218.
Related:
Acyl substitution of readily accessible α-siloxy Weinreb amides with
organolithium compounds provides diverse cross-benzoin and α-siloxy ketone
products. Enantiopure benzoins can be accessed via a chiral pool approach.
C. N. Larcombe, L. R. Malins, J. Org. Chem., 2022, 87,
9408-9413.