Categories: C-C Bond Formation > Oxygen-containing molecules > Alcohols >
Synthesis of homoallylic alcohols
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The combination of Me3SiO- and Bu4N+
serves as a general activator of organotrimethylsilanes for addition reactions.
A broad scope of bench-stable trimethylsilanes (including acetate, allyl,
propargyl, benzyl, dithiane, heteroaryl, and aryl derivatives) can be used as
carbanion equivalents for synthesis. Reactions are achieved at rt without the
requirement of specialized precautions that are commonplace for other
organometallics.
M. Das, D. F. O'Shea, J. Org. Chem., 2014,
79, 5595-5607.
AgF and (R)-DIFLUORPHOS predominantly formed a 1:1 complex that
provided high enantioselectivity for the asymmetric Sakurai-Hosomi
allylation of various simple ketones. Only 1,2-adducts were obtained from
both acyclic and cyclic conjugate ketones. Highly diastereo- and
enantioselective reactions with E- or Z-crotyltrimethoxysilane
and racemic allylsilanes are described.
M. Wadamoto, H. Yamamoto, J. Am. Chem. Soc.,
2005,
127, 14556-14557.
Chiral phosphoric acids catalyze an enantioselective addition of
bi(cyclopentyl)diol-derived boronates to aldehydes to provide homoallylic, propargylic,
and crotylic alcohols with high enantiomeric excess and diastereomeric ratios. A wide substrate scope was exhibited, and the novel boronates provided high
enantiocontrol.
J. Yuan, P. Jain, J. C. Antilla, J. Org. Chem., 2020, 85,
12988-13003.
C2-symmetric
chiral-substituted 1,16-dihedroxytetraphenylenes (DHTP) were used as organocatalysts in asymmetric allylboration
of ketones under very mild conditions. Several tertiary alcohols
were isolated in good yields with high ees.
G.-L. Chai, B. Zhu, J. Chang, J. Org. Chem., 2019, 84,
120-127.
A general allylation of a diverse array of ketones with allyl boronates is
effective with 2 mol % of a zinc alkoxide catalyst and with relatively short
reaction times. Studies of the key exchange process are presented, which support
a cyclic transition state for the boron to zinc exchange.
K. R. Fandrick, D. R. Fandrick, J. J. Gao, J. T. Reeves, Z. Tan, W. Li, J. J.
Song, B. Lu, N. K. Yee, C. H. Senanayake, Org. Lett., 2010,
12, 3748-3751.
A general and mild CuCl-TBAT-catalyzed allylation of aldehydes, ketones, and
imines was developed using allyltrimethoxysilane as the allylating reagent.
Mechanism studies indicated that the copper alkoxide,
allylfluorodimethoxysilane, and allyltrimethoxysilane are essential to
promote the reaction efficiently.
S. Yamasaki, K. Fujii, R. Wada, M. Kanai, M. Shibasaki, J. Am. Chem. Soc.,
2002,
124, 6536-6537.
A ball-milling-enabled zinc-mediated Barbier-type allylation of a broad range
of carbonyl compounds is operationally simple and does not require inert
atmospheres or dry solvents. The reaction is applicable across a range of
different zinc metal morphologies.
J. Yin, R. T. Stark, I. A. Fallis, D. L. Browne, J. Org. Chem., 2020, 85,
2347-2354.
An expanded survey of transition-metal catalysts has confirmed that cobalt salts
uniquely deliver homoallylic alcohol products from epoxides, with retention of
the original epoxide stereochemistry. A tandem Corey-Chaykovsky/epoxide
olefination sequence gives homoallylic alcohols from aldehydes.
M. L Jamieson, N. Z. Brant, M. A. Brimble, D. P. Furkert, Synthesis, 2017,
49, 3952-3956.
A cationic iridium complex-catalyzed olefin transposition of (E)-1-alkenylboronates
followed by a chiral phosphoric acid-catalyzed allylation reaction of aldehydes
enables a highly diastereo- and enantioselective synthesis of anti homoallylic
alcohols.
T. Miura, Y. Nishida, M. Morimoto, M. Murakami, J. Am. Chem. Soc., 2013,
135, 11497-11500.
A nickel complex catalyzes an allylboration of aldehydes, facilitating the
preparation of homoallylic alcohols in high diastereoselectivity. Allylation
occurs through a well-defined six-membered transition state, with nickel acting
as a Lewis acid.
F. M. Dennis, C. C. Robertson, B. M. Partridge, Synthesis, 2020, 52,
1903-1914.
A highly reactive nickel-catalyst system enables an in situ transposition of a
homoallyl pinacol boronic ester to a Z-crotyl pinacol boronic ester, that
reacts with various aldehydes to form syn-homoallylic alcohols in high
diastereoselectivities. Also, the multiple transposition of pentenyl pinacol
boronic ester was realized.
F. Weber, M. Ballmann, C. Kohlmeyer, G. Hilt, Org. Lett., 2016, 18,
548-551.
A radical strategy (1e-) through metal-hydride hydrogen atom transfer (MHAT)
using photoredox cobalt and titanium dual catalysis for aldehyde crotylation
with butadiene achieves excellent regio- and diastereoselectivity.
H. Yan, J.-R. Shan, F. Zhang, Y. Chen, X. Zhang, Q. Liao, E. Hao, L. Shi, Org. Lett., 2023, 25,
7694-7699.
1,4-Pentadiene and 1,5-hexadiene can serve as allylmetal pronucleophiles in
regio-, anti-diastereo-, and enantioselective carbonyl additions from alcohol
proelectrophiles. Primary alcohol dehydrogenation delivers a ruthenium hydride
that affects alkene isomerization to furnish a conjugated diene, followed by
transfer hydrogenative carbonyl addition.
Z. J. Dubey, W. Shen, J. A. Little, M. K. Krische, J. Am. Chem. Soc.,
2023, 145, 8576-8582.
An unprecedented cobalt-catalyzed highly site-, diastereo-, and
enantioselective protocol for stereoselective formation of nucleophilic
allyl-Co(II) complexes followed by addition to aldehydes provides diversified
enantioenriched homoallylic alcohols with a remarkably broad scope of allyl
groups that can be introduced.
L. Wang, L. Wang, M. Li, Q. Chong, F. Meng, J. Am. Chem. Soc.,
2021, 143, 12755-12765.
A highly diastereoselective Pd-catalyzed carbonyl allylation of aldehydes and
isatins with simple acyclic olefins as allylating reagents consists of a
Pd-catalyzed oxidative allylic C-H borylation and an allylboration of carbonyls
accelerated by phosphoric acid. N-Fluorobenzenesulfonimide as oxidant
plays a key role.
Z.-L. Tao, X.-H. Li, Z.-Y. Han, L.-Z. Gong, J. Am. Chem. Soc., 2015,
137, 4054-4057.
Chiral ruthenium(II) complexes catalyze a highly regio-, diastereo-, and
enantioselective reaction of alkynes with primary alcohols to form homoallylic
alcohols. In this enantioselective carbonyl allylation, alkynes serve as
allylmetal equivalents.
T. Liang, K. D. Ngyuen, W. Zhang, M. J. Krische, J. Am. Chem. Soc., 2015,
137, 3161-3164.
In RuI(CO)(η3-C3H5)(JOSIPHOS) catalyzed anti-diastereo- and
enantioselective C-C couplings of primary alcohols with 1-aryl-1-propynes, a
non-classical hydrogen bond between iodide and the aldehyde formyl CH bond
stabilizes the favored transition state for carbonyl addition. An improved
catalytic system provides previously unattainable products of carbonyl
anti-(α-aryl)allylation.
E. Ortiz, J. Z. Shezaf, Y.-H. Chang, T. P. Gonçalves, K.-W. Huang, M. J.
Krische, J. Am. Chem. Soc.,
2021, 143, 16709-16717.
The photoexcitation of Hantzsch ester can directly activate chromium reagents
through a single-electron transfer process. The synthetic application was
demonstrated through a photoredox decarboxylative allylation of aldehydes with
feedstock butadiene without exogenous photocatalysts, metallic reductants, or
additives.
S. Lin, Y. Chen, H. Yan, Y. Liu, Y. Sun, E. Hao, C. Shi, D. Zhang, N. Zhu, L.
Shi, Org. Lett., 2021, 23,
8077-8081.
Enantioselective transfer hydrogenation of 1,1-dimethylallene in the presence of
aldehydes and 2-propanol or primary alcohols without 2-propanol employing a
cyclometalated iridium C,O-benzoate derived from allyl acetate, m-nitrobenzoic
acid, and (S)-SEGPHOS delivers reverse-prenylation products in very good
yields and enantioselectivities.
S. B. Han, I. S. Kim, H. Han, M. J. Krische, J. Am. Chem. Soc., 2009,
131, 6916-6917.
General In(0)-catalyzed allylations of ketones proceeded smoothly in water under
mild conditions, and water proved to be essential for these reactions. Both the
substrate scope and the functional group tolerance were excellent. The In metal
catalyst could be easily recovered and reused without loss of catalytic activity.
U. Schneider, M. Ueno, S. Kobayashi, J. Am. Chem. Soc., 2008,
130, 13824-13825.
γ-Adducts of homoallylic alcohols were converted to the corresponding
α-adducts by an acid-catalyzed allyl-transfer reaction. In the allyl-transfer
reaction, anti- and syn-γ-adducts gave E- and Z-α-adducts, respectively, and
the optical purity was transferred to the α-adducts This suggests that the allyl-transfer reaction proceeds
stereoselectively via a six-membered cyclic transition state.
S.-i. Sumida, M. Ohga, J. Mitani, J. Nokami, J. Am. Chem. Soc., 2000,
122, 1310-1313.
Nickel catalyzes a multicomponent coupling reaction of terminal alkenes, carbon
dioxide, and organoaluminum reagents to provide homoallylic alcohols in good
yields with excellent regio- and stereoselectivities.
Y. Mori, C. Shigeno, Y. Luo, B. Chan, G. Onodera, M. Kimura,
Synlett, 2018, 29, 742-746.
A practical Ni(cod)-catalyzed three-component coupling of 1,3-butadiene,
carbonyl compounds, and arylboronic acids provides 1,4-disubstituted homoallylic
alcohols without any external base and ligand at ambient temperature. The
neutral conditions tolerate even highly base-sensitive functional groups.
Y.-Q. Li, G. Chen, S.-L. Shi, Org. Lett., 2021, 23,
2571-2577.
A Ni-catalyzed three-component cross-electrophile coupling of 1,3-dienes with
aldehydes and aryl bromides using manganese metal as the reducing agent provides
1,4-disubstituted homoallylic alcohols.
Y.-Q. Qi, S. Liu, Y. Xu, Y. Li, T. Su, H.-L. Ni, Y. Gao, W. Yu, P. Cao, P. Hu,
K.-Q. Zhao, B.-Q. Wang, B. Chen, Org. Lett.,
2022, 24, 5023-5028.
A highly selective
copper-catalyzed
reductive hydroxymethylation of 1,3-dienes with CO2 provides chiral all-carbon acyclic quaternary
stereocenters. A variety of readily
available 1,1-disubstituted 1,3-dienes, as well as a 1,3,5-triene, undergo the
reaction with high chemo-, regio-, E/Z-, and enantioselectivities
and good functional group
tolerance.
X.-W. Chen, L. Zhu, Y.-Y. Gui, K. Jing, Y.-X. Jiang, Z.-Y. Bo, Y. Lan, J. Li,
D.-G. Yu, J. Am. Chem. Soc.,
2019, 141, 18825-18835.
The use of montmorillonite clay as catalyst provides a straightforward and
scalable, highly diastereoselective method for the allylation and crotylation of
a range of ketones and aldehydes with air- and water-stable potassium allyl and
crotyltrifluoroborate salts.
F. Nowrouzi, A. N. Thadani, R. A. Batey, Org. Lett., 2009,
11, 2631-2634.
Insertion of 2-substituted dienes into the methanol C-H bond occurs in a
regioselective manner to form all-carbon quaternary centers with excellent
levels of enantioselectivity using an iridium-PhanePhos catalyst via methanol
dehydrogenation, reversible diene hydrometalation, and regioisomeric formation
of allyliridium-formaldehyde pairs.
K. D. Nguyen, D. Herkommer, M. J. Krische, J. Am. Chem. Soc., 2016,
138, 14210-14213.
(R,R)-Ph-BPE ligated Cu catalyzes a chemo-, regio-, and enantioselective allylation of ketones with
1,3-dienes in the presence a hydrosilane to provide chiral homoallylic tertiary alcohols
under very mild conditions with good functional group tolerance. 1,3-dienes as the latent
allylic nucleophiles avoid the the use of stoichiometric
quantities of allylmetal reagents.
B. Fu, X. Yuan, Y. Li, Y. Wang, Q. Zhang, T. Xiong, Q. Zhang,
Org. Lett., 2019, 21, 3576-3580.
A combined carbocupration of terminal alkynes followed by a zinc homologation
and further reaction with ketones lead, in a single-pot operation, to
homoallylic alcohols possessing two consecutive quaternary stereocenters with
excellent diastereoselectivity.
B. Dutta, N. Gilboa, I. Marek, J. Am. Chem. Soc., 2010,
132, 5588-5589.
Asymmetric allylation of aldehydes with γ-disubstituted allyl halides in the
presence of a sulfonamide/oxazoline chromium complex provides various
synthetically useful α-homoallylic alcohols with two consecutive stereogenic
centers, including one quaternary carbon, in a highly diastereoselective and
enantioselective manner.
Y. Xiong, G. Zhang, Org. Lett.,
2016, 18, 5094-5097.
In acetonitrile as solvent and in the presence of a simple cobalt halide as
catalyst, the reduction by zinc dust of a mixture of aldehydes or ketones
and allylic acetates affords the corresponding homoallylic alcohols in good
yields.
P. Gomes, C. Gosmini, J. Périchon, Synthesis,
2003, 1909-1915.
Under catalysis by ruthenium trichloride in the presence of carbon monoxide,
water, and triethylamine, a wide range of aromatic, olefinic, and aliphatic
aldehydes are efficiently allylated with allyl acetate under mild conditions.
The stoichiometric byproducts of this reaction are carbon dioxide and acetic
acid.
S. E. Denmark, S. T. Nguyen, Org. Lett., 2009,
11, 781-784.
An iridium-catalyzed coupling of 1-aryl-1-propynes with primary alcohols gives
secondary homoallylic alcohols as products. This reaction involves an
iridium-catalyzed novel catalytic transformation of 2-alkynes and primary
alcohols through the formation of hydrido(π-allyl)iridium as a possible key
intermediate.
Y. Obora, S. Hatanaka, Y. Ishii, Org. Lett., 2009,
11, 3510-3513.
Titanocene dichloride catalyzes the formation of an organozinc species via
catalytic activation of allyl halides. Nucleophilic addition to carbonyl
derivatives provides the desired homoallylic alcohols in very good yields in
short reaction times. This discovery will have wide ranging applicability in the
generation of highly reactive organometallic reagents.
L. M. Fleury, B. L. Ashfeld, Org. Lett., 2009,
11, 5670-5673.
A rapid and efficient procedure for the solvent-free synthesis of
homoallylic and homopropargyl alcohols has been achieved by zinc-mediated
Barbier-type reaction of carbonyl compounds at room temperature.
J.-X. Wang, X. Jia, T. Meng, L. Xin,
Synthesis, 2005, 2669-2672.
A range of polysubstituted allylic zinc chlorides were obtained in good yield
using a LiCl-mediated zinc dust insertion in polysubstituted allylic chlorides.
A highly diastereoselective synthesis of homoallylic alcohols bearing up to two
adjacent quaternary centers by the addition of polysubstituted allylic zinc
reagents to carbonyl compounds.
H. Ren, G. Dunet, P. Mayer, P. Knochel, J. Am. Chem. Soc., 2007,
129, 5376-5377.
A solvent- and metal-free process for the direct methallylboration of ketones
with a stable B-methallylborinane is accelerated by tertiary alcohols. In the
presence of 2.0 equiv of tert-amyl alcohol, the methallylation products
were prepared at room temperature in excellent yields. The process offers simple
operation, high efficiency, and mild reaction conditions.
Y. Zhang, N. Li, N. Goyal, G. Li, H. Lee, B. Z. Lu, C. H. Senanayake, J. Org. Chem., 2013,
78, 5775-5781.
The combination of Bi(OAc)3 and a chiral phosphoric acid catalyzes
a highly efficient asymmetric 1,2-allylation reaction of β,γ-unsaturated
α-ketoesters under mild conditions. A subsequent anionic oxy-Cope rearrangement
achieves an asymmetric formal 1,4-allylation reaction in a one-pot process.
X.-S. Liu, Y. Li, X. Li, Org. Lett., 2021, 23,
9128-9133.
Cu-catalyzed highly regio- and stereoselective 1,4-protoboration of
dienylboronates provides unsymmetrical 1,4-bifunctional allylboron reagents. A
subsequent chemoselective allylboration with aldehydes followed by oxidative
workup give diol products with high diastereoselectivity.
S. Gao, M. Wang, M. Chen, Org. Lett.,
2018, 20, 7921-7925.
An enantioselective nickel-catalyzed borylative coupling of
1,3-dienes with aldehydes provides an efficient route to highly valuable
homoallylic alcohols in a single step. Enabled
by a chiral spiro phosphine-oxazoline nickel complex, this transformation yields
products with exceptional diastereoselectivity, E-selectivity, and
enantioselectivity.
J.-T. Ma, T. Zhang, B.-Y. Yao, L.-J. Xiao, Q.-L. Zhou, J. Am. Chem. Soc.,
2023, 145, 19195-19201.
An enantioselective nickel-catalyzed borylative coupling of
1,3-dienes with aldehydes provides an efficient route to highly valuable
homoallylic alcohols in a single step. Enabled
by a chiral spiro phosphine-oxazoline nickel complex, this transformation yields
products with exceptional diastereoselectivity, E-selectivity, and
enantioselectivity.
J.-T. Ma, T. Zhang, B.-Y. Yao, L.-J. Xiao, Q.-L. Zhou, J. Am. Chem. Soc.,
2023, 145, 19195-19201.
A chiral α-borylmethyl-(Z)-crotylboronate reagent enables highly stereo- and
enantioselective syntheses of (E)-δ-hydroxymethyl-syn-homoallylic
alcohols via aldehyde allylboration and a subsequent oxidative workup.
J. Liu, S. Gao, M. Chen, Org. Lett., 2021, 23,
9451-9456.
Racemic homoallenyl alcohols can be synthesized from aldehydes and
chloroprene-derived Grignards. The use of bis[2-dimethylaminoethyl]ether (BDMAEE)
as an additive at low temperatures shifts the selectivity of the reaction almost
exclusive toward allene formation. Simple and more elaborate methods for further
derivatization enable quick access to more complex structures.
A. G. A. Geissler, B. Breit, Org. Lett., 2021, 23,
2621-2625.
Cu-catalyzed allylation of aldehydes or ketones with α-vinyl allylboronate
provides secondary or tertiary δ-vinyl-homoallylic alcohols with high E-selectivities.
It is proposed that the reaction operates under the Curtin-Hammett principle via
the intermediacy of an α-vinyl allylic copper species.
J. Liu, B. Su, M. Chen, Org. Lett., 2021, 23,
6035-6040.
Copper(I) catalyzes a regioselective asymmetric allylation of ketones with
commercially available 1,4-pentadiene as a pronucleophile to provide a variety
of chiral tertiary alcohols bearing a terminal (Z)-1,3-diene in high (Z)/(E)
ratio and high enantioselectivity. The synthetic utility of the product is
demonstrated by a copper(I)-catalyzed regioselective borylation of the 1,3-diene
group.
F. Zhong, Z.-Z. Pan, S.-W. Zhou, H.-Jun. Zhang, L. Yin, J. Am. Chem. Soc.,
2021, 143, 4556-4562.
A regio- and stereoselective nickel-catalyzed three-component coupling
reaction of aldehydes, 1,3-dienes, and alkenylzirconium afforded skipped diene
compounds bearing various functionals and heterocyclic groups. The products were
readily transformed into structurally diverse polyenes.
C.-G. Wang, Y. Zhang, S. Wang, B. Chen, Y. Li, H.-L. Ni, Y. Gao, P. Hu, B.-Q.
Wang, P. Cao, Org. Lett., 2021, 23,
535-541.
An In(III)-catalyzed intermolecular glyoxylate-ene reaction enables an efficient
synthesis of homoallylic alcohols with high enantioselectivities and anti-diastereoselectivities.
Only alkene isomers having a proton β-cis to the substituent reacted in this
catalytic system.
X. Zhang, M. Wang, R. Ding, Y.-H. Xu, T.-P. Loh, Org. Lett.,
2015,
17, 2736-2739.
In situ generation of allylic boronates by iridium-catalyzed borylation of
cyclic alkenes in the presence of additives, such as methylimidazole and DBU,
followed a reaction with aldehydes allows the synthesis of stereodefined
homoallylic alcohols. Cycloalkenes without additives as well as acyclic
substrates gave vinylic boronates, which were coupled with organohalides in a
Suzuki-Miyaura sequence.
V. J. Olsson, K. J. Szabó, J. Org. Chem., 2009,
74, 7715-7723.
A regio- and diastereoselective nickel-catalyzed reductive coupling of
carbonyls with dienes in the presence of a stoichiometric amount of
bis(pinacolato)diboron furnishes allyl boronic esters as the reaction product,
which was readily converted to the derived allylic alcohol by oxidative workup.
H. Y. Cho, J. P. Morken, J. Am. Chem. Soc., 2008,
130, 16140-16141.
Trapping of β,γ-alkynyl aldehydes, generated in situ by treatment of alkynyloxiranes with a
catalytic amount of Sc(OTf)3 or BF3ˇOEt2, by a variety of allyl nucleophiles affords homopropargylic
homoallylic alcohols in good yield and selectivity. Subsequent enyne metathesis
gives functionalized vinylcyclopentenols.
L. Wang, M. L. Maddess, M. Lautens, J. Org. Chem., 2007,
72, 1822-1825.
The palladium catalyzed decarboxylative asymmetric allylic alkylation of allyl
1,2-enediol carbonates gives exclusively α-hydroxyketones in very good yields
and high enantiomeric excesses using Lnaph as ligand in DME. The
reaction proceeds under extremely mild conditions and tolerates a broad range of
esters.
B. M. Trost, J. Xu, T. Schmidt, J. Am. Chem. Soc., 2008,
130, 11852-11853.
In a new, efficient, catalytic asymmetric protocol for the synthesis of
α-tertiary hydroxyaldehydes from readily available α-halo or α-hydroxy ketones
or enol silyl ethers, the chiral ligand controls the regioselectivity as well as
the enantioselectivity.
B. M. Trost, J. Xu, M. Reichle, J. Am. Chem. Soc., 2007,
129, 282-283.
Chiral α-(carbamoyloxy)alkylcopper reagents, prepared using Hoppe's sBuLi/(-)-sparteine
methodology and subsequent transmetalations with ZnCl2 and CuCN,
reacted with various electrophiles to give enantiomerically pure alcohols after
deprotection.
J. P. N. Papillon, R. J. K. Taylor, Org. Lett., 2002, 4,
119-122.
Highly stereoselective 2-oxonia-Cope rearrangement reactions between
rationally designed nonracemic vinylogous aldolation synthons and aldehydes
provide δ-hydroxy-α,β-unsaturated esters with excellent enantioselectivities and
unprecedented Z- and E-selectivities.
A. Padarti, H. Han, Org. Lett.,
2018, 20, 1448-1452.
Highly stereoselective 2-oxonia-Cope rearrangement reactions between
rationally designed nonracemic vinylogous aldolation synthons and aldehydes
provide δ-hydroxy-α,β-unsaturated esters with excellent enantioselectivities and
unprecedented Z- and E-selectivities.
A. Padarti, H. Han, Org. Lett.,
2018, 20, 1448-1452.
A novel nickel(II)-N,N′-dioxide complex facilitated the asymmetric
synthesis of biologically interesting α-hydroxy carbonyl compounds under mild
conditions by highly enantioselective carbonyl-ene reactions of glyoxal
derivatives with various alkenes. Various aromatic, aliphatic, and
heteroaromatic glyoxal derivatives, as well as glyoxylate, were tolerated.
K. Zheng, J. Shi, X. Liu, X. Feng, J. Am. Chem. Soc., 2008,
130, 15770-15771.
Highly enantioselective carbonyl-ene reactions of various 1,1-disubstituted and
trisubstituted alkenes with ethyl glyoxylate are catalyzed by a new Co-salen
complex under nearly ideal conditions at room temperature using low catalyst
loadings. The reaction provides chiral, homoallylic alcohol products in
excellent yields, enantioselectivities, and diastereoselectivities.
G. E. Hutson, A. H. Dave, V. H. Rawal, Org. Lett., 2007,
9, 3869-3872.
3-Substituted-2-alkoxycarbonyl allylboronates are readily produced by the
cross-coupling of Baylis-Hillman acetate adducts and bis(pinacolato)diboron in
the presence of a palladium catalyst. Subsequent addition of excess aqueous KHF2
gives stable allyl trifluoroborate salts. Allylboronate and allyltrifluoroborate
derivatives react stereoselectively with aldehydes to afford functionalized
homoallylic alcohols.
G. W. Kabalka B. Venkataiah, G. Dong, J. Org. Chem., 2004,
69, 5807-5809.
A highly regioselective vinylogous aldol reaction catalyzed by SiCl4
and a chiral phosphoramide, provides δ-hydroxy enones for a variety of
aldehyde and dienol ether structures in good yields, excellent
enantioselectivities, and in some cases excellent anti
diastereoselectivities.
S. E. Denmark, G. L. Beutner, J. Am. Chem. Soc., 2003,
125, 7800-7801.
The weakly acidic species, silicon tetrachloride (SiCl4), can be
activated by binding of a strongly Lewis basic chiral phosphoramide, leading
to in situ formation of a chiral Lewis acid for catalysis of the aldol
reaction of silyl ketene acetals and silyl dienol ethers (vinylogous aldol
reactions) to conjugated and nonconjugated aldehydes. The high levels of
regio-, anti
diastereo-, and enantioselectivity observed are discussed.
S. E. Denmark, G. L. Beutner, T. Wynn, M. D. Eastgate, J. Am. Chem. Soc.,
2005,
127, 3774-3789.
N,O-Silyl dienyl ketene acetals are useful reagents for highly
enantioselective vinylogous aldol additions to various aldehydes in the
presence of SiCl4 and the catalytic action of a chiral
phosphoramide.
S. E. Denmark, J. R. Heemstra, Jr., J. Am. Chem. Soc.,
2006,
128, 1038-1039.
Highly diastereo- and enantioselective syntheses of 1,5-disubstituted (E)-1,5-anti-pent-2-endiols
and (Z)-1,5-syn-pent-2-endiols have been achieved via the
one-pot coupling of two different aldehydes with bifunctional
γ-boryl-substituted allylborane reagents, which were generated in situ by
the hydroboration of allenes with diisopinocampheylborane. The
stereospecificity is discussed.
E. M. Flamme, W. R. Roush, J. Am. Chem. Soc., 2002,
124, 13644-13645.
Addition of α-alkenylzirconacyclopentenes to aldehyde enables a highly
stereoselective synthesis of β-hydroxyallenes with multiple stereogenic centers
including allenic axial chirality, as well as center chirality. Remarkably, the
reaction occurs with completely different chemoselectivity in comparison with
the usual alkyl- or aryl-substituted zirconacyclopentenes.
Y. Zhou, J. Chen, C. Zhao, E. Wang, Y. Liu, Y. Li, J. Org. Chem., 2009,
74, 5326-5330.
A nucleophilic allylation of acylsilanes in water provides versatile
functionalized tertiary α-silyl alcohols in high yields with the assistance of
hydrogen bonding. Unlike the conventional strategy, transition metals and an
additional Lewis acid catalyst were not required.
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A highly regio- and stereoselective palladium-catalyzed synthesis of various
2-silylallylboronates from allenes and
2-(dimethylphenylsilanyl)-4,4,5,5-tetramethyl[1,3,2]dioxaborolane afforded
the corresponding silaboration products in moderate to excellent yields. In
the absence of an organic iodide, the silaboration gives products having
completely different regiochemistry. In the presence of an aldehyde, the
silaboration reaction afforded homoallylic alcohols in one pot in good to
excellent yields, with exceedingly high syn selectivity.
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Enantioselective Allylic Carbon-Carbon Bond Construction |