Synthesis of substituted α,β-unsaturated compounds
Iron-catalyzed cross-coupling of Grignard reagents with (E)- and (Z)-enol tosylates proceeded smoothly to give a variety of the corresponding (E)- and (Z)-trisubstituted α,β-unsaturated methyl esters in good yield. The simple, mild, stereoretentive method utilized iron(III) chloride and other iron salts as catalyst.
H. Nishikado, H. Nakatsuji, K. Ueno, R. Nagase, Y. Tanabe, Synlett, 2010, 2087-2092.
The reaction of alkynes with Ni(cod)2 and CO2 gave a nickelacycle, which was reacted with various organozinc reagents under very mild conditions to provide β,β‘-disubstituted, α,β-unsaturated carboxylic acids in a highly regio- and stereoselective manner.
M. Takimoto, K. Shimizu, M. Mori, Org. Lett., 2001, 3, 3345-3347.
A Pd-catalyzed oxidative cross-coupling reaction of arylboronic acids with α-diazoesters using molecular oxygen as the reoxidant gives E-α,β-diarylacrylates in good yields and very high E-to-Z selectivity.
Y.-T. Tsoi, Z. Zhou, A. S. C. Chan, W.-Y. Yu, Org. Lett., 2010, 12, 4506-4509.
An sp3 C-H bond-transformation reaction of methylarenes provides the corresponding allylbenzene derivatives in good yields in the presence of tetrabutylammonium iodide and tert-butyl hydroperoxide at 80 °C.
F. Shahsavari, A. Abbasi, M. Ghaznafarpour-Darjjani, S. M. Ghafelebashi, M. Daftari-Besheli, Synlett, 2017, 28, 1646-1648.
A practical, highly enantioselective reaction of readily available 1,3-dienes and alkyl acrylates provides valuable, enantio-pure skipped 1,4-diene esters in the presence of commercially available cobalt salts and chiral ligands. This hetero-dimerization reaction tolerates various organic functional groups (e.g., aromatic substituents, halides, isolated mono- and di-substituted double bonds, esters, silyl ethers, and silyl enol ethers).
S. M. Jing, V. Balasanthiran, V. Pagar, J. C. Gallucci, T. V. Rajanbabu, J. Am. Chem. Soc., 2017, 139, 18034-18043.
A ruthenium-catalyzed chelation-assisted C-H bond activation of aromatic ketones followed by reaction with olefins provides Heck-type products in good to excellent yields with a high regio- and stereoselective manner.
K. Padala, M. Jeganmohan, Org. Lett., 2011, 13, 6144-6147.
A copper-catalzed functionalization of propiolate esters with various Grignard reagents in presence of trimethylsilyl trifluoromethanesulfonate enables the synthesis of substituted E-vinyl silanes in good yields and excellent diastereoselectivities via a catalytic carbocupration-silicon group migration sequence.
A. J. Mueller Hendrix, M. P. Jennings, Org. Lett., 2010, 12, 2750-2753.
A stereoselective approach towards ethyl-substituted conjugated dienoic esters utilising a Suzuki cross-coupling reaction has been achieved. In addition, a method for their conversion into the corresponding ethyl ketones is presented.
D. Keck, T. Muller, S. Bräse, Synlett, 2006, 3457-3460.
A radical carbozincation of diethyl acetylenedicarboxylate in the presence of air leads to fumaric derivatives through a selective alkylzinc group radical transfer controlled by coordination. The total trans stereocontrol is unprecedented, carbocupration is well-known to give the reversal selectivity at low temperature, while classical radical addition methodologies lead to mixtures of isomers.
J. Maury, L. Feray, M. P. Bertrand, Org. Lett., 2011, 13, 1884-1887.
An intermolecular reductive coupling of ynoates and aldehydes in the presence of a silane using catalytic amounts of Ni(COD)2, an N-heterocyclic carbene ligand, and PPh3 delivers invaluable silyl-protected γ-hydroxy-α,β-enoates. This methodology provides a quick entry to many other 1,4-difunctional compounds and oxygen-containing five-membered rings. The intermediacy of metallacycles in the catalytic process has been established.
S. K. Rodrigo, H. Guan, J. Org. Chem., 2012, 77, 8303-8309.
N-heterocyclic carbenes catalyze intramolecular β-alkylations of α,β-unsaturated esters, amides, and nitriles that bear pendant leaving groups to form a variety of ring sizes. The mechanism is discussed.
C. Fischer, S. W. Smith, D. A. Powell, G. C. Fu, J. Am. Chem. Soc., 2006, 128, 1472-1473.
Highly regioselective Heck couplings of α,β-unsaturated tosylate and mesylate derivatives with N-acyl N-vinylamines and vinyl ethers were achieved. This method provides a cheap alternative to similar couplings using a triflate electrophile.
A. L. Hansen, T. Skrydstrup, Org. Lett., 2005, 7, 5585-5587.
|Copper-Catalyzed Conjugate Addition to α,β-Unsaturated Carbonyl Compounds|