Synthesis of allyl alcohols
A catalytic regio- and stereoselective 1,4-hydroboration with pinacolborane in the presence of Ni(cod)2 and PCy3 exhibits broad substrate scope operating on a range of substituted 1,3-dienes and occurs with generally high levels of selectivity and efficiency. The intermediate allylboronate can be oxidized to stereodefined allylic alcohols or can be used in stereoselective carbonyl addition reactions.
R. J. Ely, J. P. Morken, J. Am. Chem. Soc., 2010, 132, 2534-2535.
Use of 4,5-diazafluorenone as an ancillary ligand for Pd(OAc)2 enables terminal alkenes to be converted to linear allylic acetoxylation products in good yields and selectivity under O2. Mechanistic studies have revealed that the ligand facilitates C-O reductive elimination from a π-allyl-PdII intermediate, thereby eliminating the requirement for benzoquinone as stoichiometric oxidant in this key catalytic step.
A. N. Campbell, P. B. White, I. A. Guzei, S. S. Stahl, J. Am. Chem. Soc., 2010, 132, 15116-15119.
Pd(OAc)2, sulfoxide-oxazoline (sox) as a ligand and benzoquinone as an oxidant enable a ligand-controlled branch-selective allylic C-H carboxylation. The developed catalytic system couples terminal alkenes and carboxylic acids to furnish the corresponding branched allylic esters with high regioselectivity.
H. Kondo, F. Yu, J. Yamaguchi, G. Liu, K. Itami, Org. Lett., 2014, 16, 4212-4215.
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.
An oxidative decarboxylation of β,γ-unsaturated carboxylic acids mediated by PhI(OAc)2 gives the corresponding allylic acetates. In addition, a decarboxylative C-N bond formation was achieved. Mechanistic studies suggest an unique reactivity of hypervalent iodine reagents in this ionic oxidative decarboxylation.
K. Kiyokawa, S. Yahata, T. Kojima, S. Minakata, Org. Lett., 2014, 16, 4646-4649.
A Pd(TFA)2-catalyzed 1,3-isomerization of tertiary allylic alcohols gives secondary allylic alcohols. In a one-pot procedure, a subsequent Pd(TFA)2/neocuproine-catalyzed oxidation leads to β-disubstituted-α,β-unsaturated enones directly.
J. Li, C. Tan, J. Gong, Z. Yang, Org. Lett., 2014, 16, 5370-5373.
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.
The combination of a vanadium-oxo compound with a lipase enables the regio- and enantioconvergent transformation of racemic allyl alcohols into optically active allyl esters. In this dynamic kinetic resolution, the vanadium compounds catalyzes both the racemization and the transposition of the hydroxyl group, while the lipase effects the chemo- and enantioselective esterification.
S. Akai, R. Hanada, N. Fujiwara, Y. Kita, M. Egi, Org. Lett., 2010, 12, 4900-4903.
Trichloroacetimidates of allylic alcohols, either generated in situ or in a separate step, undergo clean enantioselective SN2′ substitution with various carboxylic acids in the presence of a chiral palladium(II) catalyst. The scope and limitations of this useful catalytic asymmetric allylic esterification are defined.
J. S. Cannon, S. F. Kirsch, L. E. Overman, J. Am. Chem. Soc., 2010, 132, 15185-15191.
The cooperative interaction of a diselane and a photoredox catalyst enables a metal-free protocol for the oxidative coupling of nonactivated alkenes with simple carboxylic acids in ambient air or pure O2 as the terminal oxidant. A range of both functionalized and nonfunctionalized alkenes can be readily converted into the corresponding allylic ester with good yields and excellent regioselectivity as well as good functional group tolerance.
S. Ortgies, C. Depken, A. Breder, Org. Lett., 2016, 18, 2856-2859.
Chiral phosphine-catalyzed coupling of two readily available partners, γ-aryl-substituted alkynoates and alcohols, under mild conditions enables the enantioselective synthesis of benzylic ethers via internal redox reaction of the alkynoate partner.
D. T. Ziegler, G. C. Fu, J. Am. Chem. Soc., 2016, 138, 12069-12072.
A copper(II)-catalyzed intermolecular three-component oxyarylation of allenes using arylboronic acids as a carbon source and TEMPO as an oxygen source proceeded under mild conditions with high regio- and stereoselectivity and functional group tolerance.
T. Itoh, Y. Shimizu, M. Kanai, Org. Lett., 2014, 16, 2736-2739.
A general, Ir(I)-catalyzed enantioselective decarboxylative allylic etherification of aryl allyl carbonates provides aryl allyl ethers with high stereoselection.
D. Kim, S. Reddy, O. V. Singh, J. S. Lee, S. B. Kong, H. Han, Org. Lett., 2013, 15, 512-515.
The allylic oxidation of cyclic alkenes with a copper-aluminum mixed oxide as catalyst in the presence of a carboxylic acid and tert-butyl hydroperoxide as the oxidant gives the corresponding allylic esters. When l-proline is employed, the allylic alcohol or ketone is obtained.
A. L. García-Cabeza, R. Marín-Barrios, F. J. Moreno-Dorado, M. J. Ortega, G. M. Massanet, F. M. Guerra, Org. Lett., 2014, 16, 1598-1601.
An enzyme acylation catalyst and a heterogeneous Brřnsted acid as an isomerization/racemization catalyst enables a migratory dynamic kinetic resolution of readily available carbocyclic tertiary carbinols to yield allylic esters in high yield with excellent stereoselectivity. An easy-to-use teabag setup combining resin-bound catalysts, a biphasic isooctane-water solvent system, and a highly lipophilic acyl donor efficiently suppresses side reactions.
C. M. Sapu, T. Görbe, R. Lihammar, J.-E. Bäckvall, J. Deska, Org. Lett., 2014, 16, 5952-5955.
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.
Pt-catalyzed enantioselective addition of bis(pinacolato)diboron (B2(pin)2) to conjugated dienes enables an asymmetric 1,4-dihydroxylation of 1,3-dienes. Dienes which are unable to adopt the S-cis conformation are unreactive. For most substrates, 1,4-addition is the predominant pathway.
H. E. Burks, L. T. Kliman, J. P. Morken, J. Am. Chem. Soc., 2009, 131, 9134-9135.
A catalytic stereoselective 1,4-diboration of conjugated dienes with B2(pin)2 and the presence of Ni(cod)2 and PCy3 as the catalyst roceeds efficiently at low catalyst loadings and broadens the substrate scope of current methods for catalytic diene diboration by including internal and sterically hindered. The intermediate allylboronate was oxidized to the stereodefined allylic 1,4-diol.
R. J. Ely, J. P. Morken, Org. Lett., 2010, 12, 4348-4351.
An enantioselective 1,4-diboration of cyclic dienes with a new taddol-derived phosphonite ligand and subsequent oxidation delivers 1,4-diols with excellent enantioselectivity, whereas homologation can be used to deliver chiral 1,6-diols.
K. Hong, J. P. Morken, J. Org. Chem., 2011, 76, 9102-9108.
The presence of a base strongly improves the efficiency and the selectivity of the Pd-catalyzed oxidation of terminal alkenes in carboxylic acids. The methodology is particularly well adapted for the oxidation of homoallylic alcohols, for which the resulting acyloxylated products are obtained selectively as E-isomers in good yields.
E. Thiery, C. Aouf, J. Belloy, D. Harakat, J. Le Bras, J. Muzart, J. Org. Chem., 2010, 75, 1771-1774.
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.
A method for the preparation of a wide range of branched allylic esters from terminal alkynes proceeds via a redox-neutral propargylic CH activation employing a rhodium(I)/DPEphos catalyst.
A. Lumbroso, P. Koschker, N. R. Vautravers, B. Breit, J. Am. Chem. Soc., 2011, 133, 2386-2389.
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.
Gold N-heterocyclic carbene complexes, in conjunction with a silver salt, were found to efficiently catalyze the rearrangement of allylic acetates under both conventional and microwave-assisted heating. The steric hindrance of the ligand bound to gold was found crucial as only extremely bulky ligands permitted the isomerization.
N. Marion, R. Gealageas, S. P. Nolan, Org. Lett., 2007, 9, 2653-2656.
Efficient and stereoselective rearrangement catalyzed by only one mole-percent gold(I) chloride/silver(I) trifluoromethanesulfonate of Baylis-Hillman acetates afforded 2-(acetoxymethyl)alk-2-enoates under mild reaction conditions in very good yields with 100% E-selectivity.Cyclohex-2-enone derived Baylis-Hillman acetates gave 2-alkylidenecyclohex-3-enones by elimination of acetic acid.
Y. Liu, D. Mao, J. Qian, S. Lou, Z. Xu, Y. Zhang, Synthesis, 2009, 1170-1174.
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.
In the presence of a 1:1 mixture of n-butyllithium and lithioacetonitrile in THF, a series of styrene oxides can be converted into one-carbon homologated allyl alcohols in an unusual regioselective manner.
T. Tomioka, R. Sankranti, T. Yamada, C. Clark, Org. Lett., 2013, 15, 5099-5101.
The combination of PdCl2 and DMA allows highly effective oxygenation of terminal olefins under cocatalyst-free conditions. The use of a different nucleophile (H2O, AcOH) can lead to a complete switch in regioselectivity between C1 and C2 positions.
T. Mitsudome, T. Umetani, N. Nosaka, K. Mori, T. Mizugaki, K. Ebitani, K. Kaneda, Angew. Chem. Int. Ed., 2006, 45, 481-485.