Categories: C=C Bond Formation >
Synthesis of alkenes by isomerizations
Recent Literature
An effective Pd-catalyzed isomerization of terminal olefins with 2-PyPPh2
as the ligand provides trans-2-olefins bearing various functional groups
with high regio- and stereoselectivity under mild reaction conditions. The
ligand is crucial for the reaction.
W. Ren, F. Sun, J. Chu, Y. Shi,
Org. Lett., 2020, 22, 1868-1873.
A ruthenium complex is a very efficient catalyst for selective
mono-isomerization of various multifunctional alkenes to afford E-products.
Many reactions are complete within 10 min at room temperature. Even sensitive
enols and enamides susceptible to further reaction can be generated. Very low
catalyst loadings can be employed.
C. R. Larsen, D. B. Grotjahn, J. Am. Chem. Soc., 2012,
134, 10357-10360.
A β-dialdiminate-supported, high-spin cobalt(I) complex can convert terminal
alkenes, including allylbenzenes, to Z-2-alkenes with unprecedentedly
high regioselectivity and stereoselectivity. Deuterium labeling studies indicate
that the catalyst operates through a π-allyl mechanism.
D. Kim, G. Pillon, D. J. DiPrimio, P. L. Holland, J. Am. Chem. Soc.,
2021, 143, 3070-3074.
A stepwise PCET activation of thermodynamically stable olefins is mediated by
an excited-state oxidant and a Brønsted base to afford an allylic radical that
is captured by a Cr(II) cocatalyst to furnish an allylchromium(III) intermediate.
In situ protodemetalation of this allylchromium complex by methanol is highly
regioselective and affords an isomerized and less thermodynamically stable
alkene product.
K. Zhao, R. R. Knowles, J. Am. Chem. Soc.,
2022, 144, 137-144.
An
operationally simple, atom-economical, and efficient cobalt-catalyzed migrational isomerization of styrenes
provides trisubstituted alkenes. Even with very low catalyst
loadings, the reaction could be conducted in neat and completed in 1 h with
excellent conversion and high E stereoselectivity.
J. Zhao, B. Cheng, C. Chen, Z. Lu,
Org. Lett., 2020, 22, 837-841.
Cobalt complexes catalyze an isomerization of 1,1-disubstituted alkenes as an
alternative stereoselective approach to trisubstituted alkenes. This protocol
exhibits a good functional group tolerance and scalability. The high
stereoselectivity of the reaction is attributed to both a π-π stacking effect
and the steric hindrance between substrate and catalyst.
S. Zhang, D. Bedi, L. Cheng, D. K. Unruh, G. Li, M. Findlater, J. Am. Chem. Soc.,
2020, 142, 8910-8917.
Catalytic access to thermodynamically less stable Z-alkenes have relied upon
kinetic control of the reaction. A mild and simple orthogonal approach proceeds
via photochemically catalyzed isomerization of the thermodynamic E-alkene
to the less stable Z-isomer via a photochemical pumping mechanism.
K. Singh, S. J. Staig, J. D. Weaver, J. Am. Chem. Soc., 2014,
136, 5275-5278.
The use of an amido-diphosphine ligand enables an efficient cobalt-catalyzed
Z to E isomerization of β-substituted styrenes with good
functional tolerance and high stereoselectivity. The reaction could be scaled up
to gram-scale with a catalyst loading of 0.1 mol %.
H. Liu, M. Xu, C. Cai, J. Chen, Y. Gu, Y. Xia,
Org. Lett., 2020, 22, 1193-1198.
A rhodium complex catalyzes the synthesis of E-alkenes from E/Z mixtures of alkenes
in the presence of B2pin2 under mild reaction conditions.
The reaction offers broad functional
group tolerance and has great application potential.
H. Yang, W. Dong, W. Wang, T. Li, W. Zhao, Synthesis, 2020, 52,
2833-2840.
Hexaisobutyryl reduced cercosporin (HiBRCP) is a highly efficient organic
photosensitizer for the promotion of E to Z isomerization of
alkenes. Moreover, an energy-transfer-mediated nickel catalysis in the presence
of HiBRCP enabled cross-coupling of aryl bromides and carboxylic acids.
Y. Zhang, M. Xia, M. Li, Q. Ping, Z. Yuan, Y. Liu, H. Yin, S. Huang, Y. Rao, J. Org. Chem., 2021, 86,
15284-15297.
The combination of a CoCl2 precatalyst with an amido-diphosphine-oxazoline
ligand catalyzes the geometrical isomerization of E/Z mixtures of
1,3-dienes to afford (E) isomers in high stereoselectivity. This facile
transformation offers a broad substrate scope with good functional group
tolerance and could be scaled up to gram scale.
W. Wang, S. He, Y. Zhong, J. Chen, C. Cai, Y. Luo, Y. Xia, J. Org. Chem., 2022, 87,
4712-4723.
A cobalt-catalyzed multipositional isomerization of conjugated dienes is
operationally simple and atom-economical using readily available starting
materials with an E:Z mixture to access disubstituted 1,3-dienes with
excellent yields and good E,E stereoselectivity. A mechanism via alkene
insertion of cobalt hydride species and β-H elimination of a π-allyl cobalt
intermediate is proposed.
J. Zhao, G. Xu, X. Wang, J. Liu, X. Ren, X. Hong, Z. Lu, Org. Lett.,
2022, 24, 4592-4597.
A riboflavin-mediated highly (Z)-selective and operationally simple,
catalytic isomerization has been applied to a variety of enone-derived
substrates. The reaction can also be used for the synthesis of the medically
relevant 4-substituted coumarin scaffold.
J. B. Metternich, R. Gilmour, J. Am. Chem. Soc., 2015,
137, 11254-11257.
Zwitterionic organocatalysts with an amide anion/iminium cation charge pair
catalyze the isomerization of maleic acid diesters to give fumaric acid diesters.
Whereas the cooperative effect of the charges lower the activation barrier for a
Michael addition of the catalyst to the substrate, the key interaction results
from a nonclassical hydrogen bond.
Y.-P. Lam, Z. Lam, Y.-Y. Yeung, J. Org. Chem., 2021, 86,
1183-1190.
Hot water as a mildly acidic catalyst efficiently promoted 1,n-rearrangement
(n = 3, 5, 7, 9) of allylic alcohols. In some cases, the rearrangement reactions
joined isolated C-C double or triple bonds to generate conjugated polyene or
enyne structure motifs. The polyene natural product navenone B has been
constructed by iterative use of a Grignard reaction, a 1,3-rearrangement of the
resulting allylic alcohol, and subsequent oxidation.
P.-F. Li, H.-L. Wang, J. Qu, J. Org. Chem., 2014,
79, 3955-3962.
Commercially available and very inexpensive benzoic acids catalyze an efficient
and simple isomerization of readily prepared allylic alcohols to yield cyclic
products, unusual enyne, and dienols. The catalysts can be tuned for reactivity
and substrate sensitivity.
J. A. McCubbin, S. Voth, O. V. Krokhin, J. Org. Chem., 2011,
76, 8537-8542.
O3ReOSiPh3 promotes the 1,3-isomerization of various
allylic alcohols. Two different strategies allow the selective formation of
a single isomer. The first strategy utilizes the formation of a conjugated
alkene to ensure a high selectivity. The second strategy employs N,O-bis(trimethylsilyl)acetamide
(BSA) as an additive to remove the product from the reaction equilibrium and
works well for the isomerization of tertiary allylic alcohols.
C. Morrill, R. H. Grubbs, J. Am. Chem. Soc.,
2005, 127, 2842-2843.
C. Morrill, R. H. Grubbs, J. Am. Chem. Soc.,
2005, 127, 2842-2843.
An efficient Z-selective oxidative isomerization process of allyl ethers
catalyzed by a cobalt(II) (salen) complex using N-fluoro-2,4,6-trimethylpyridinium
trifluoromethanesulfonate (Me3NFPY•OTf) as an oxidant provides
thermodynamically less stable Z-enol ethers in excellent yields with high
geometric control. Diallyl ethers can also be isomerized at room temperature.
G. Huang, M. Ke, Y. Tao, F. Chen, J. Org. Chem., 2020, 85,
5321-5329.
Lithium diisopropylamide (LDA) promotes virtually quantitative conversion of
allylic ethers to (Z)-propenyl ethers with very high stereoselectivity in
THF at room temperature. The reaction time for the conversion increases with
more sterically hindered allylic ethers.
C. Su, P. G. Williard, Org. Lett., 2010,
12, 5378-5381.
Substituted benzofurans were synthesized from their corresponding substituted
1-allyl-2-allyloxybenzenes using ruthenium-catalyzed C- and O-allyl
isomerization followed by ring-closing metathesis.
W. A. L. van Otterlo, G. L. Morgans, L. G. Madeley, S. Kuzvidza, S. S. Moleele,
N. Thornton, C. B. de Koning, Tetrahedron, 2005,
61, 7746-7755.
A hydroxyl group-directed, highly regio- and stereoselective transposition of
allylic alcohols based on rhenium catalysis is suitable for a direct
isomerization of acetals into the thermodynamically preferred isomer as long as
one of the hydroxyl groups is allylic. This method will expand the scope of
rhenium-catalyzed alcohol transpositions for complex molecule synthesis.
A. T. Herrmann, T. Saito, C. E. Stivala, J. Tom, A. Zakarian, J. Am. Chem. Soc., 2010,
132, 5962-5963.
Ruthenium hydrides promote the positional isomerization of 1,3-dienes into more
highly substituted 1,3-dienes in a stereoconvergent manner. The reaction can
also be conducted in one pot starting with an ene-yne metathesis of terminal
alkynes and alkenes and a subsequent decomposition of the Grubbs catalyst into a
ruthenium hydride, which promotes the dienyl isomerization.
J. R. Clark, J. R. Griffiths, S. T. Diver, J. Am. Chem. Soc., 2013,
135, 3327-3330.
A biphenyl-2-ylphosphine with a basic amino group at the 3′ position possesses
orthogonally positioned "push" and "pull" forces, that enable a
gold(I)-catalyzed soft propargylic deprotonation and permit the bridging of a
difference of >26 pKa units (in DMSO) between a propargylic hydrogen and a
protonated tertiary aniline. This design led to efficient isomerization of
alkynes into versatile 1,3-dienes with synthetically useful scope under mild
reaction conditions.
Z. Wang, Y. Wang, L. Zhang, J. Am. Chem. Soc., 2014,
136, 8887-8890.
A unique palladium hydride complex generated from a simple Pd source and boric
acid [B(OH)3] enables a redox neutral rearrangement of an allene to a
1,3-diene.
Y. Al-Jawaheri, M. Turner, M. C. Kimber, Synthesis, 2018, 50,
2329-2336.
Pd(PPh3)4-catalyzed isomerization of
methylenecyclopropanes (MCPs) proceeds smoothly
at 80°C in acetic acid and toluene to give 1-substituted or 1,1-disubstituted
dienes in good to excellent yields. The mechanism is discussed.
M. Shi, B.-Y. Wang, J.-W. Huang, J. Org. Chem., 2005, 70, 5606-5610.
Aryl-substituted cyclopropyl carbinol derivatives undergo a facile
stereoselective rearrangement catalyzed by In(OTf)3 in
dichloromethane under sonication to produce the substituted conjugated all-trans-butadienes.
B. C. Ranu, S. Banerjee, Eur. J. Org. Chem., 2006, 3012-3015.
The Crabtree’s reagent catalyzes the isomerization of N-sulfonyl
2,2-disubstituted aziridines to allyl amines under mild conditions without activation of the catalyst by
hydrogen.
A. Cabré. G. Sciortino, G. Ujaque, X. Verdaguer, A.
Lledós, A. Riera, Org. Lett.,
2018, 20, 5747-5751.
Efficient alkene isomerizations of readily available 1,1-disubstituted
alkenylboronate esters provide synthetically valuable trisubstituted
alkenylboronates. Either stereoisomer of the target alkenylboronate motif can be
obtained by employing different isomerization catalysts.
L. Segura, I. Massad, M. Ogasawara, I. Marek, Org. Lett., 2021, 23,
9194-9198.
A cobalt-catalyzed regioselective olefin isomerization reaction with
fine-tunable NNP-pincer ligand structures features high kinetic control of
regioselectivity. This mild catalytic system enables the isomerization of
1,1-disubstituted olefins bearing a wide range of functional groups in excellent
yields and regioselectivity.
X. Liu, W. Zhang, Y. Wang, Z.-X. Zhang, L. Jiao, Q. Liu, J. Am. Chem. Soc.,
2018,
140, 6873-6882.
A strain-inducing positional alkene isomerization reaction provides mild and
selective access to cyclobutene building blocks from readily obtained
cyclobutylidene precursors. This endergonic isomerization relies on the
sequential and synergistic action of a decatungstate polyanion photocatalyst and
cobaloxime co-catalyst to store potential energy in the form of ring strain.
V. Palani, A. E. Wendlandt, J. Am. Chem. Soc.,
2023, 145, 20053-20061.
| Related:
|
