Categories: C-C Bond Formation > Carbocyclic compounds > Cyclic alcohols
Synthesis of cyclohexanols
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For highly stereoselective reductions of a large number of five- and
six-membered cyclic ketones to the most thermodynamically stable alcohols,
ketones are treated with lithium dispersion and either FeCl2·4H2O
or CuCl2·2H2O in THF at room temperature. This protocol is
more convenient and efficient than those commonly reported for similar
reductions.
N. Kennedy, T. Cohen, J. Org. Chem.,
2015,
80, 8134-8141.
The combination of hydrogen atom transfer photocatalysis and boronic acid mediated
transient thermodynamic control enables a selective epimerization of cyclic
trans
diols to provide the less stable cis products. A range of substitution patterns and
ring sizes are amenable to selective isomerization, including stereochemically
complex polyols.
C. J. Oswood, D. W. C. MacMillan, J. Am. Chem. Soc.,
2022, 144, 93-98.
Catalytic enone hydrometallation represents a promising strategy for enolate
generation, circumventing the utilization of preformed enol or enolate
derivatives. Metal-catalyzed reductive condensation of α,β-unsaturated carbonyl compounds with aldehydes in the presence of a hydride donor enables highly
diastereoselective aldol and Michael cycloreductions.
T.-G. Baik, A. L. Luis, L.-C. Wang, M. J. Krische, J. Am. Chem. Soc., 2001,
123, 5112-5113.
A tandem 1,4-reduction-aldol cyclization is induced by exposure of monoenone
monoketones to catecholborane in THF at ambient temperature. Six-membered cyclic
aldol products are formed in excellent yield with high levels of syn
diastereoselectivity for aromatic and heteroaromatic enones. Five-membered ring
formation proceeds less readily, but the yield is improved through addition of
Rh(I) salts.
R. R. Huddleston, D. F. Cauble, M. J. Krische, J. Org. Chem., 2003,
68, 11-14.
Treatment of β,β-disubstituted-α,β-unsaturated ketones bearing a ketone residue
with in situ generated, catalytic CuH ligated by a nonracemic ligand leads to
cyclic aldol products with three newly created adjacent chiral centers.
Excellent diastereoselectivities and enantioselectivities are obtained for
several examples studied.
B. H. Lipshutz, B. Amorelli, J. B. Unger, J. Am. Chem. Soc., 2008,
130, 14378-14379.
B. H. Lipshutz, B. Amorelli, J. B. Unger, J. Am. Chem. Soc., 2008,
130, 14378-14379.
A highly enantioselective catalytic protocol for the intramolecular reductive
coupling of ketones and hydrazones furnishes cyclic syn 1,2-amino alcohol
derivatives with excellent levels of diastereo- and enantioselectivity. The
reaction proceeds through neutral ketyl radical intermediates generated via a
concerted proton-coupled electron transfer event jointly mediated by a chiral
phosphoric acid catalyst and a photoredox catalyst.
L. J. Rono, H. G. Yayla, D. Y. Wang, M. F. Armstrong, R. R. Knowles, J. Am. Chem. Soc., 2013,
135, 17735-17738.
An efficient lithium amide-induced intramolecular cyclopropanation of
bishomoallylic and trishomoallylic epoxides is described. The methodology is
used in an asymmetric synthesis of sabina ketone.
D. M. Hodgson, Y. K. Chung, J.-M. Paris, J. Am. Chem. Soc., 2004,
126, 8654-8655.