Carboxylation, synthesis of benzoates and benzamides
Only 1-5 mol % of CO are needed to enable a Pd-catalyzed hydroxycarbonylation of aryl iodides, bromides, and chlorides in the presence of potassium formate as the only stoichiometric, mildly basic nucleophile and a reservoir of CO. The substoichiometric CO is generated in situ from an acyl-Pd(II) precatalyst, which provides both the CO and an active catalyst, and thereby obviates the need for handling the toxic gas.
S. Korsager, R. H. Taaning, T. Skrydstrup, J. Am. Chem. Soc., 2013, 135, 2891-2894.
A ligand-free palladium-catalyzed hydroxycarbonylation of aryl halides provides the corresponding aromatic carboxylic acids in high yields with high selectivity at room temperature and atmospheric pressure. The new method is operationally simple and scalable. In addition, aromatic esters were easily synthesized through hydroxycarbonylation followed by a one-pot alkylation with alkyl halides.
W. Han, F. Jin, Q. Zhou, Synthesis, 2015, 47, 1861-1868.
A palladium-catalyzed carbonylative transformation of organic halides with formic acid as the coupling partner provides carboxylic acids in the presence of a catalytic amount of DCC as the activator. Both vinyl and aryl (pseudo)halides were conveniently transformed into the corresponding acids in good yields.
F.-P. Wu, J.-B. Peng, X. Qi, X.-F. Wu, J. Org. Chem., 2017, 82, 9710-9714.
A nickel-catalyzed carboxylation of aryl and vinyl chlorides proceeds under a CO2 pressure of 1 atm at room temperature in the presence of nickel catalysts and Mn powder as a reducing agent. Various aryl chlorides and vinyl chlorides could be converted to the corresponding carboxylic acid in good yields.
T. Fujihara, K. Nogi, T. Xu, J. Terao, Y. Tsuji, J. Am. Chem. Soc., 2012, 134, 9106-9109.
A combination of Pd(OAc)2 as a carboxylation catalyst and Ir(ppy)2(dtbpy)(PF6) as a photoredox catalyst enables a highly useful, visible-light-driven carboxylation of aryl bromides and chlorides under 1 atm of CO2 in high yields. This carboxylation reaction proceeds with various functionalized aryl bromides and chlorides without the necessity of using stoichiometric metallic reductants.
K. Shimomaki, K. Murata, R. Martin, N. Iwasawa, J. Am. Chem. Soc., 2017, 139, 9467-9470.
An efficient generation of a stoichiometric amount of carbon monoxide by Zn-mediated reduction of oxalyl chloride can replace the use of excess toxic gaseous CO in palladium-catalyzed alkoxy-/amino-/hydrogen-/hydroxycarbonylation processes providing esters, amides, aldehydes, and carboxylic acids in very good yields.
M. Markovič, P. Lopatka, P. Koóš, T. Gracza, Org. Lett., 2015, 17, 5618-5621.
Phosphonium bromide ionic liquids are superior media in the carbonylation of aryl and vinyl halides. Formation of acid bromide intermediates was detected in control experiments providing an extended view on the overall catalytic cycle involved. Solvent-free product isolation and recycling of the ionic liquid containing active Pd-catalyst are also demonstrated.
J. McNulty, J. J. Nair, A. Robertson, A. Lei, Org. Lett., 2007, 9, 4575-4578.
A highly efficient cobalt-catalyzed reductive carboxylation reaction of alkenyl trifluoromethanesulfonates (triflates) enables the synthesis of α,β-unsaturated carboxylic acids in the presence of Mn powder as a reducing reagent under 1 atm pressure of CO2 at room temperature. Moreover, the carboxylation of sterically hindered aryl triflates proceeds smoothly in the presence of a nickel or cobalt catalyst.
K. Nogi, T. Fujihara, J. Terao, Y. Tsuji, J. Org. Chem., 2015, 80, 11618-11623.
A mild, functional group tolerant palladium-catalyzed carbonylation of aryl chlorides using atmospheric pressure of carbon monoxide allows the preparation of phenyl esters, alkyl esters and carboxylic acids. Phenyl esters are shown to be useful acylating agents, delivering libraries of carbonyl derivatives, including alkyl, allyl and thioesters, under very mild conditions.
D. A. Watson, X. Fan, S. L. Buchwald, J. Org. Chem., 2008, 73, 7096-7101.
A highly reactive silyl anion, which is generated from a strained four-membered ring disilane (3,4-benzo-1,1,2,2-tetraethyldisilacyclobutene) and CsF mediates the formation of carbanions from a wide range of aryl, alkenyl, alkynyl, benzyl, allyl, and alkyl halides. The resulting anionic species can be trapped with CO2 to produce carboxylic acids with high efficiency.
T. Mita, K. Suga, K. Sato, Y. Sato, Org. Lett., 2015, 17, 5276-5279.
A near-stoichiometric amount of N-Formylsaccharin, an easily accessible crystalline compound, has been employed as an efficient CO source in a mild Pd-catalyzed fluorocarbonylation of aryl halides to afford the corresponding acyl fluorides in high yields. The acyl fluorides obtained could be readily transformed into various carboxylic acid derivatives such as carboxylic acid, esters, thioesters, and amides in a one-pot procedure.
T. Ueda, H. Konishi, K. Manabe, Org. Lett., 2013, 15, 5370-5373.
A highly efficient palladium-catalyzed carbonylation of aryl, alkenyl, and allyl halides with phenyl formate affords one-carbon-elongated carboxylic acid phenyl esters in excellent yields. The reaction proceeds smoothly under mild conditions, avoids the use of carbon monoxide, and tolerates a wide range of functional groups including aldehyde, ether, ketone, ester, and cyano groups.
T. Ueda, H. Konishi, K. Manabe, Org. Lett., 2012, 14, 3100-3103.
Mo(CO)6 mediates the alkoxycarbonylation of aryl halides as catalyst and source of CO in the presence of alcohols to afford arenecarboxylic acid esters. This convenient procedure proceeds with a small excess of carbon monoxide in the form of Mo(CO)6 and avoids the use of excess gaseous carbon monoxide. Using this procedure, various carboxylic acid esters were prepared.
W. Ren, A. Emi, M. Yamane, Synthesis, 2011, 2261-2267.
Pd-catalyzed decarboxylative cross-coupling of aryl iodides, bromides, and chlorides with potassium oxalate monoesters is potentially useful for laboratory-scale synthesis of aryl and alkenyl esters. Bulky, electron-rich bidentate phosphine ligands are preferred in the reaction, whereas Cu is not needed for decarboxylation.
R. Shang, Y. Fu, J.-B. Li, S.-L. Zhang, Q.-X. Guo, L. Liu, J. Am. Chem. Soc., 2009, 131, 5738-5739.
A system derived from Pd(OAc)2 and the bulky, bidentate dcpp ligand catalyzes the carbonylation of aryl tosylates and mesylates to form esters under atmospheric CO pressure and temperatures of 80-110°C. A broad substrate scope allows carbonylation of electron-rich, electron-poor, and heterocyclic tosylates and mesylates, and the reaction shows wide functional group tolerance.
R. H. Munday, J. R. Martinelli, S. L. Buchwald, J. Am. Chem. Soc., 2008, 130, 2754-2755.
Potassium methyl carbonate serves as a versatile carboxylating agent of allyl- and arylboronic esters in copper-catalyzed synthesis of carboxylic acids.
H. A. Duong, T. M. Nguyen, N. Z. B. Rosman, L. J. L. Tan, Synthesis, 2014, 46, 1881-1885.
A copper(I)-catalyzed carboxylation reaction of aryl- and alkenylboronic esters under CO2 showed wide generality with higher functional group tolerance compared to the corresponding Rh(I)-catalyzed reaction.
J. Takaya, K. Ukai, N. Iwasawa, Org. Lett., 2008, 10, 2697-2700.
Treatment of 2,2-dimethylpropan-1,3-diol esters of aryl- and alkenylboronic acids with a catalytic amount of [Rh(OH)(cod)]2 in the presence of 1,3-bis(diphenylphosphino)propane and CsF in dioxane at 60°C under carbon dioxide atmosphere gave carboxylic acids in good yields.
K. Ukai, M. Aoki, J. Takaya, N. Iwasawa, J. Am. Chem. Soc., 2006, 128, 8706-8707.
The reaction of readily accessible and bench-stable substituted S-phenyl thiocarbamates and Grignard reactants provides secondary amides. Oxidative workup allows recycling of the thiolate leaving group. This amide synthesis is especially suitable for the preparation of challenging amides.
P. Mampuys, E. Ruijter, R. V. A. Orru, B. U. W. Maes, Org. Lett., 2018, 20, 4235-4239.
N-Boc- and N-Cbz-protected amines can be directly converted into amides by a novel rhodium-catalyzed coupling with arylboroxines. Both protected anilines and aliphatic amines are efficiently transformed into a wide variety of secondary benzamides, including sterically hindered and electron-deficient amides. The reaction tolerates acid-labile and reducible functional groups.
D. S. W. Lim, T. T. S. Lew, Y. Zhang, Org. Lett., 2015, 17, 6054-6057.
The use of N-methoxymethyl-N-organylcarbamoyl(trimethyl)silanes as secondary amides source enables a direct transformation of aryl halides into the corresponding secondary aromatic amides via palladium-catalyzed aminocarbonylation. The reaction tolerates a broad range of functional groups except for steric hindrance.
W. Tong, P. Cao, Y. Liu, J. Chen, J. Org. Chem., 2017, 82, 11603-11608.
In a simple, Mo-mediated carbamoylation reaction of aryl halides, the incorporation of carbon monoxide is so efficient that it requires only a slight excess amount of carbon monoxide in the form of its molybdenum complex, Mo(CO)6. The reaction is applicable for the synthesis of a wide variety of not only secondary and tertiary amides but also primary amides by using aqueous ammonia.
W. Ren, M. Yamane, J. Org. Chem., 2010, 75, 8410-8415.
An efficient and practical molybdenum-mediated carbonylation of aryl and heteroaryl halides with a variety of nucleophiles using microwave irradiation offers a wide scope and proceeds in good to excellent yields.
B. Roberts, D. Liptrot, L. Alcaraz, T. Luker, M. J. Stocks, Org. Lett., 2010, 12, 4280-4283.
A new and efficient palladium-catalyzed C-C coupling of aryl halides with isocyanides enables the synthesis of amides under mild conditions. This transformation could extend its use to the synthesis of natural products and significant pharmaceuticals.
H. Jiang, B. Liu, Y. Li. A. Wang, H. Huang, Org. Lett., 2011, 13, 1028-1031.
A transition-metal-free carboxyamidation process, using aryl diazonium tetrafluoroborates and isocyanides under mild conditions, is initiated by a base and solvent induced aryl radical, followed by radical addition to isocyanide and single electron transfer (SET) oxidation. The reaction affords the corresponding arylcarboxyamide upon hydration of the nitrilium intermediate.
Z. Xia, Q. Zhu, Org. Lett., 2013, 15, 4110-4113.
An operationally simple hydroxycarbonylation of aryl and vinyl triflates to the corresponding carboxylic acids with a palladium-mediated microwave system was carried out in water.
G. Lesma, A. Sacchetti, A. Silvani, Synthesis, 2006, 594-596.
Sonication of a mixture of magnesium powder, 1,2-dibromoethane, aryl bromide and diethyl dicarbonate in THF followed by treatment with BF3·OEt2 at room temperature afforded aryl ester with reasonable yield. A series of aryl bromides were investigated and transformed to their corresponding aryl esters.
A. S.-Y. Lee, C.-C. Wu, L.-S. Lin, H.-F. Hsu, Synthesis, 2004, 568-572.
Regioselective halogen-metal exchange reactions using isopropylmagnesium chloride were carried out on 3-substituted 1,2-dibromo arenes.
K. Menzel, L. Dimichele, P. Mills, D. E. Frantz, T. D. Nelson, M. H. Kress, Synlett, 2006, 1948-1952.
The Pd-catalyzed coupling of ortho-substituted arylboronic esters with carbamoyl chlorides gives tertiary benzamides in good yield.
M. Lysen, S. Kelleher, M. Betrup, J. L. Kristensen, J. Org. Chem., 2005, 70, 5342-5343.
Nickel catalysis enables a very efficient aminocarbonylation reaction to be performed between aryl iodides or bromides and N,N-dimethylformamide (DMF) in the presence of sodium methoxide and a phosphite ligand, which is very stable to air and moisture and, furthermore, inexpensive.
J. Ju, M. Jeong, J. Moon, H. M. Jung, S. Lee, Org. Lett., 2007, 9, 4615-4618.
Tertiary amides can be synthesized by a palladium-catalyzed coupling of N,N-dimethylformamide with aryl or alkenyl halides in the presence of phosphoryl chloride.
K. Hosoi, K. Nozaki, T. Hiyama, Org. Lett., 2002, 4, 2849-2851.
A carbon-monoxide-free aminocarbonylation of various N-substituted formamides with aryl iodides and aryl bromides using palladium acetate and Xantphos is applicable for a wide range of formamides and aryl halides containing different functional groups furnishing good to excellent yield of the corresponding products.
D. N. Sawant, Y. S. Wagh, K. D. Bhatte, B. M. Bhanage, J. Org. Chem., 2011, 76, 5489-5494.
A palladium-catalyzed cross-coupling reaction between organoboronic acids and commercially available N-methoxy-N-methylcarbamoyl chloride allows the synthesis of Weinreb benzamides and heteroaromatic analogues, as well as α,β-unsaturated Weinreb amides. This simple protocol is also applicable to the use of potassium organotrifluoroborates.
R. Krishnamoorthy, S. Q. Lam, C. M. Manley, R. J. Herr, J. Org. Chem., 2010, 75, 1251-1258.
Cycloadditions of Diels-Alder dienophiles containing linked enyne sites, each substituted with activating groups, occurred specifically at the acetylenic center. A remote acrylyl group bound to the olefinic site totally dominated the regiochemical course of the cycloaddition. Explanations for these findings at the computational level are provided.
M. Dai, D. Sarlah, M. Yu, S. J. Danishefsky, G. O. Jones, K. N. Houk, J. Am. Chem. Soc., 2007, 129, 645-657.
A simple and straightforward method for the direct carboxylation of aromatic heterocylces such as oxazoles, thiazoles, and oxadiazoles using CO2 as the C1 source requires no metal catalyst and only Cs2CO3 as the base. A good functional group tolerance is achieved.
O. Vechorkin, N. Hirt, X. Hu, Org. Lett., 2010, 12, 3567-3569.
The combination of thiols as nucleophiles and a bidentate ligand enable a palladium-catalyzed thiocarbonylation of styrene derivatives with high regioselectivity toward the more valuable branched isomer. The ambient reaction conditions (temperature, catalyst loading) and the use of a CO surrogate render this transformation a useful method for the synthesis of thioesters.
V. Hirschbeck, P. H. Gehrtz, I. Fleischer, J. Am. Chem. Soc., 2016, 138, 16794-16799.