Categories: C-N Bond Formation >
Synthesis of carbamates
The arylation of N-H and O-H containing compounds at room temperature with phenylboronic acids is promoted in the presence of cupric acetate and a tertiary amine. Substrates include phenols, amines, anilines, amides, imides, ureas, carbamates, and sulfonamides.
D. M. T. Chan, K. L. Monaco, R.-P. Wang, M. P. Winteres, Tetrahedron Lett., 1998, 39, 2933-2936.
An efficient synthesis of aryl carbamates - including major carbamate protecting groups - was achieved by introducing alcohols into the reaction of palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate. This methodology also provides direct access to S-thiocarbamates and diisocyanate precursors to polyurethane materials.
E. V. Vinogradova, N. H. Park, B. P. Fors, S. L. Buchwald, Org. Lett., 2013, 15, 1394-1397.
The reaction of azidoformates with boronic acids in the presence of 10 mol% of copper chloride enables a mild and efficient synthesis of N-arylcarbamates in an open flask at room temperature without additional base, ligand, or additive. A subsequent reaction with aluminum-amine complexes in a two-step one-pot procedure gives N-arylcarbamates.
S.-Y. Moon, U. Bin Kim, D.-B. Sung, W.-S. Kim, J. Org. Chem., 2015, 80, 1856-1865.
The use of PhINTs as a reagent enables a mild Hofmann rearrangement of aromatic and aliphatic carboxamides. The mild reaction conditions and high selectivity in the reaction of carboxamides with PhINTs allow the isolation of the initially formed labile isocyanates or their subsequent conversion to stable carbamates by treatment with alcohols.
A. Yoshimura, M. W. Luedtke, V. V. Zhdankin, J. Org. Chem., 2012, 77, 2087-2091.
Catalysts generated from Pd2(dba)3 and biphenyl ligands efficiently promote the coupling of amides and carbamates with unactivated vinyl triflates and tosylates, to provide enamides in good to excellent yields.
M. C. Willis, G. N. Brace, I. P. Holmes, Synthesis, 2005, 3229-3234.
The AuCl3-PPh3-catalyzed direct three-component Mannich reactions of aryl aldehydes, aryl ketones, and carbamates led to N-protected β-aryl-β-amino ketones.
L.-W. Xu, C.-G. Xia, L. Li, J. Org. Chem., 2004, 69, 8482-8484.
A direct reaction between carbamates and achiral allylic carbonates to form branched, conveniently protected primary allylic amines with high regioselectivity and enantioselectivity occurs without base in the presence of a metalacyclic iridium catalyst containing a labile ethylene ligand.
D. J. Weix, D. Marković, M. Ueda, J. F. Hartwig, Org. Lett., 2009, 11, 2944-2947.
Iridium-catalyzed allylation of potassium trifluoroacetamide or the highly reactive ammonia equivalent lithium di-tert-butyliminodicarboxylate forms a range of conveniently protected, primary, α-branched allylic amines in high yields, high branched-to-linear regioselectivities, and high enantiomeric excess.
M. J. Pouy, A. Leitner, D. J. Weix, S. Ueno, J. F. Hartwig, Org. Lett., 2007, 9, 3949-3952.
Alkylcarboxamides can be converted to the respective alkylcarbamates by Hofmann rearrangement using hypervalent iodine species generated in situ from PhI and Oxone in methanol. In addition, substituted benzamides can be converted to the respective quinone derivatives by treatment with Oxone and iodobenzene in aqueous acetonitrile.
A. A. Zagulyaeva, C. T. Banek, M. S. Yusubov, V. V. Zhdankin, Org. Lett., 2010, 12, 4644-4647.
Hofmann rearrangement of carboxamides to carbamates using Oxone as an oxidant can be efficiently catalyzed by iodobenzene via hypervalent iodine species generated in situ in the presence of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) in aqueous methanol solutions. Under these conditions, Hofmann rearrangement of various carboxamides affords corresponding carbamates in high yields.
A. Yoshimura, K. R. Middleton, M. W. Luedtke, C. Zhu, V. V. Zhdankin, J. Org. Chem., 2012, 77, 11399-11404.
A versatile and efficient copper-catalyzed amidation of vinyl bromides and iodides has been developed. The protocol, which uses a combination of copper iodide and N,N'-dimethyl ethylenediamine, tolerates substrates bearing ester, silyl ether, and amino groups.
L. Jiang, G. E. Job, A. Klapars, S. L. Buchwald, Org. Lett., 2003, 5, 3667-3669.
A mild, ruthenium-catalyzed anti-Markovnikov addition of secondary amides, anilides, lactames, ureas, bislactames, and carbamates to terminal alkynes has been developped. Two complementary protocols provide either the E or the Z isomers.
L. J. Goossen, J. E. Rauhaus, G. Deng, Angew. Chem. Int. Ed., 2005, 44, 4042-4045.
A range of enol triflates can be coupled with amides, carbamates, and sulfonamides using palladium catalysis. This method allows the synthesis of enamides, which may not be readily available by other means.
D. J. Wallace, D. J. Klauber, C.-Y. Chen, R. P. Volante, Org. Lett., 2003, 5, 4749-4752.
A facile route to ynamides in high yields was achieved through an iron-catalyzed C-N coupling reaction of amides with alkynyl bromides in the presence of 20 mol % of N,N′-dimethylethane-1,2-diamine (DMEDA).
B. Yao, Z. Liang, T. Niu, Y. Zhang, J. Org. Chem., 2009, 74, 4630-4633.
An efficient palladium-catalyzed homocoupling reaction of 2-bromo-1-iodoalkenes gives 1,3-diynes. Moreover, ynamides can be synthesized in high yields from 2-bromo-1-iodoalkenes and carbamates using nanoparticulate copper(I) oxide as catalyst.
J. Xue, M.-T. Luo, Y.-L. Wen, M. Ye, L.-X. Liu, Z.-W. Chen, Synthesis, 2014, 46, 3191-3198.
Rhodium(II) azavinyl carbenes, which are conveniently generated from 1-sulfonyl-1,2,3-triazoles, undergo a facile, mild, and convergent formal 1,3-insertion into N-H and O-H bonds of primary and secondary amides, various alcohols, and carboxylic acids to afford a wide range of vicinally bisfunctionalized (Z)-olefins with perfect regio- and stereoselectivity.
S. Chuprakov, B. T. Worrell, N. Selander, R. K. Sit, V. V. Fokin, J. Am. Chem. Soc., 2014, 136, 195-202.
CeCl3 • 7H2O/NaI supported on neutral alumina (Al2O3) promotes heteroatom Michael additions under solvent-free conditions. The CeCl3 • 7H2O/NaI/Al2O3 system works well for hetero-Michael additions of weak nucleophiles such as imidazoles and carbamates to various acceptors.
G. Bartoli, M. Bartolacci, A. Giuliani, E. Marcantoni, M. Massaccesi, E. Torregiani, J. Org. Chem., 2005, 70, 169-174.
An efficient palladium-catalyzed asymmetric amination of 2,3-allenyl phosphates with nitrogen nucleophiles such as amines, hydroxylamines, and imides can be performed in presence of SEGPHOS or MeOBIPHEP ligand, affording the corresponding optically active 1-aminated derivatives with high enantiomeric excess.
Y. Imada, M. Nishida, K. Kutsuwa, S.-I. Murahashi, T. Naota, Org. Lett., 2005, 7, 5837-5839.