A simple method for the chemo- and regioselective, direct catalytic allylic alkylation of aldehydes and cyclic ketones has been developed. The combination of palladium and enamine catalysis furnished α-allylic alkylated aldehydes and cyclic ketones in high yields.
I. Ibrahem, A. Córdova, Angew. Chem. Int. Ed., 2006, 45, 1952-1956.
A highly enantioselective Pd/chiral acid-catalyzed α-allylation of α-branched aldehydes with an allyl amine as the allylating species creates all-carbon quaternary stereogenic centers in high yields and enantioselectivities.
S. Mukherjee, B. List, J. Am. Chem. Soc., 2007, 129, 11336-11337.
A highly enantioselective rhodium-catalyzed allylic alkylation of prochiral α,α-disubstituted aldehyde enolates with allyl benzoate provides acyclic quaternary carbon stereogenic centers.
T. B. Wright, P. A. Evans, J. Am. Chem. Soc., 2016, 138, 15303-15306.
A copper-catalyzed cross-coupling of substituted allylboronic acids with α-diazoketones is highly regioselective, providing the branched allylic product. The process involves creation of a new C(sp3)–C(sp3) bond by retaining the keto functional group of the α-diazoketone precursor.
A. Das, D. Wang, M.-C. Belhomme, K. J. Szabo, Org. Lett., 2015, 17, 4754-4757.
Hydrogen-bond-activated C-N bond cleavage enables Pd-catalyzed allylic alkylation of allylic amines with carbonyl compounds in inexpensive methanol as solvent. The method allows the conversion of a series of allylic amines and carbonyl compounds with excellent results.
X. Zhao, D. Liu, H. Guo, Y. Liu, W. Zhang, J. Am. Chem. Soc., 2011, 133, 19354-19357.
A fully stereodivergent, dual catalytic α-allylation of linear aldehydes proceeds via direct iridium-catalyzed substitution of racemic allylic alcohols with enamines generated in situ. The use of an Ir(P,olefin) complex and a diarylsilyl prolinol ether as catalysts in the presence of dimethylhydrogen phosphate as the promoter is crucial for achieving high enantio- and diastereoselectivity.
S. Krautwald, M. A. Schafroth, D. Sarlah, E. M. Carreira, J. Am. Chem. Soc., 2014, 136, 3020-3023.
Cyclopentanone as an electron pair donor proved highly efficient for the stabilization of allyl and vinyl cations in combination with a calcium-based catalyst system. The system enabled a transition-metal-free intermolecular carbohydroxylation of alkynes with allyl and propargyl alcohols.
T. Stopka, M. Niggemann, Org. Lett., 2015, 17, 1437-1440.
A Rh(I)/DPPF system enables a chemo- and regioselective intermolecular decarboxylative addition of β-ketoacids to terminal allenes, in which tertiary and quaternary carbon centers were formed with exclusively branched selectivity under mild conditions. Preliminary mechanism studies support that the decarboxylation follows the carbon-carbon bond formation and the reaction occurs in an outer-sphere mechanism.
C. Li, B. Breit, J. Am. Chem. Soc., 2014, 136, 650-652.
A combination of [Ir(COD)Cl]2 and a phosphoramidite ligand is an efficient catalytic system for a highly regio- and enantioselective decarboxylative alkylation of γ-substituted allyl β-ketocarboxylates, affording branched products with a regioselectivity of up to 99:1 and 96% ee.
H. He, X.-J. Zheng, Y. Li, L.-X. Dai, S.-L. You, Org. Lett., 2007, 9, 4339-4341.
In the “deacylative allylation”, the coupling partners, ketone pronucleophiles and readily available allylic alcohols undergo in situ retro-Claisen activation to generate an allylic acetate and a carbanion. In the presence of palladium, these reactive intermediates undergo catalytic coupling to form a new C-C bond.
A. J. Grenning, J. A. Tunge, J. Am. Chem. Soc., 2011, 133, 14785-14794.
Catalytic enantioselective examples of the Tsuji allylation using enol carbonates and enol silanes gave products possessing a quaternary stereogenic center, which are useful building blocks for synthetic chemistry.
D. C. Behenna, B. M. Stoltz, J. Am. Chem. Soc., 2004, 126, 15044-15045.
A catalytic enantioconvergent synthesis of quaternary stereocenters from racemates with quaternary stereocenters has been developed. A chiral Pd catalyst is involved in both the stereoablative (C-C bond-breaking) and stereoselective (C-C bond-forming) steps.
J. T. Mohr, D. C. Behenna, A. M. Harned, B. M. Stoltz, Angew. Chem. Int. Ed., 2005, 44, 6924-6927.
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.
Stereodefined enol derivatives of aldehydes are prepared from terminal alkynes through Cp2ZrCl2-catalyzed methylalumination and subsequent oxygenation with peroxyzinc species and electrophilic trapping with carboxylic anydrides. The tandem carbometalation/oxygenation tolerates free and protected alcohols, heterocycles, olefins, and nitriles.
J. R. DeBergh, K. M. Spivey, J. M. Ready, J. Am. Chem. Soc., 2008, 130, 7828-7829.