Synthesis of O-Heterocycles
An efficient and highly enantioselective Payne-type oxidation of N-sulfonyl imines exhibits broad substrate generality and unique chemoselectivity based on the combined use of hydrogen peroxide and trichloroacetonitrile under the catalysis of P-spiro chiral triaminoiminophosphorane.
D. Uraguchi, R. Tsutsumi, T. Ooi, J. Am. Chem. Soc., 2013, 135, 8161-8164.
A cobalt-catalyzed peroxidation of silyl enol ethers with molecular oxygen and triethylsilane provides silyl monoperoxyketals in good yield. These compounds serve as precursors to peroxycarbenium ions, which undergo annulations to provide 1,2-dioxolanes.
B. Hurlocker, M. R. Miner, K. A. Woerpel, Org. Lett., 2014, 16, 4280-4283.
A nickel-catalyzed double carboxylation of internal alkynes proceeds under CO2 (1 atm) at room temperature in the presence of a nickel catalyst, Zn powder as a reducing reagent, and MgBr2 as an indispensable additive. Various internal alkynes could be converted to the corresponding maleic anhydrides in good to high yields.
T. Fujihara, Y. Horimoto, T. Mizoe, F. B. Sayyed, Y. Tani, J. Terao, S. Sakaki, S. Tsuji, Org. Lett., 2014, 16, 4960-4963.
Highly functionalized δ-lactones were produced in the presence of a catalytic amount of the Cu(OAc)2-DIFLUORPHOS complex through three-component assembly of dialkylzincs, allenic esters, and unactivated ketones. This CAMCR (catalytic asymmetric multicomponent reaction) constructs two C-C bonds and one tetrasubstituted chiral center simultaneously.
K. Oisaki, D. Zhao, M. Kanai, M. Shibasaki, J. Am. Chem. Soc., 2007, 129, 7439-7443.
A BINOLate-zinc complex prepared in situ from Et2Zn and 3,3'-dibromo-BINOL is an efficient catalyst for the enantioselective hetero-Diels-Alder reaction of Danishefsky's diene with aldehydes to give 2-substituted 2,3-dihydro-4H-pyran-4-ones in up to quantitative yield and 98% ee.
H. Du, J. Long, J. Hu, X. Li, K. Ding, Org. Lett., 2002, 4, 4349-4352.
A new type of chromium-salen complex bearing DIANANE (endo,endo-2,5-diaminonorbornane) has been applied to the hetero-Diels-Alder reaction of Danishefskys diene with various aldehydes. The reactions afford the corresponding 2-substituted 2,3-dihydro-4H-pyran-4-ones in high yields and enantioselectivities.
A. Berkessel, N. Vogl, Eur. J. Org. Chem., 2006, 5029-5035.
A rhodium-catalyzed cycloisomerization converts various acyclic enynes to their cyclic diene isomers with endoselectivity. Two different catalyst systems have been developed, which are effective in promoting the C-C bond-forming cyclization of enynes to furnish carbo- and heterocycles in good to excellent yield. The mechanism is discussed.
H. Kim, C. Lee, J. Am. Chem. Soc., 2005, 127, 10180-10181.
A cyclization of N-alkenylamides catalyzed by iodoarenes under oxidative conditions enables the preparation of five-, six-, and seven-membered rings with a range of substitutions. Preliminary data from the use of chiral iodoarenes as precatalysts show that enantiocontrol is feasible.
A. Alhalib, S. Kamouka, W. J. Moran, Org. Lett., 2015, 17, 1453-1456.
A solvent- and metal-free regioselective cyclization affords 1,4-oxazine and 1,4-oxazepine derivatives as exo-dig products. Substrates for the cyclization step can be produced in a highly diastereomeric fashion by Grignard reaction as key synthetic step following Cram’s rule.
J. K. Vandavasi, W.-P. Hu, H.-Y. Chen, G. C. Senadi, C.-Y. Chen, J.-J. Wang, Org. Lett., 2012, 14, 3134-3137.
A general synthesis of various oxetan-3-ones uses readily available propargylic alcohols as substrates and proceeds without the exclusion of moisture or air. The facile formation of the strained oxetane ring provides strong support for the intermediacy of α-oxo gold carbenes. This safe and efficient generation of gold carbenes offers an entry into α-oxo metal carbene chemistry without using hazardous diazo ketones.
L. Ye, W. He, L. Zhang, J. Am. Chem. Soc., 2010, 132, 8550-8551.
An expedient and reliable method for accessing reactive α-oxo gold carbenes via gold-catalyzed intermolecular oxidation of terminal alkynes offers a safe and economical alternative to strategies based on diazo substrates. Its synthetic potential is demonstrated by expedient preparation of dihydrofuran-3-ones containing a broad range of functional groups.
L. Ye, L. Cui, G. Zhang, L. Zhang, J. Am. Chem. Soc., 2010, 132, 3258-3259.
A wide screening of substrates in ring-closing metathesis reactions reveals the great efficiency of phosphabicyclononane (phoban)-containing ruthenium-based pre-catalysts. Comparison of the catalytic activities with Grubbs' first-generation pre-catalyst illustrates the key role of the Phoban ligand.
F. Boeda, H. Clavier, M. Jordaan, W. H. Meyer, S. P. Nolan, J. Org. Chem., 2008, 73, 259-263.
Δ3-Aryl/heteroaryl substituted heterocycles via sequential Pd-catalysed termolecular cascade/ring closing metathesis (RCM)
H. A. Dondas, B. Clique, B. Cetinkaya, R. Grigg, C. Kilner, J. Morris, V. Sridharan, Tetrahedron, 2005, 61, 10652-10666.
A novel palladium-catalyzed oxidative, intramolecular cyclocarbonylation provides an efficient and direct approach for the construction of valuable 1,3,4-oxadiazole-2(3H)-ones and their derivatives.
F. Ji, X. Li, W. Guo, W. Wu, H. Jiang, J. Org. Chem., 2015, 80, 5713-5718.
A highly efficient ruthenium-catalyzed stereospecific N-demethylative rearrangement of isoxazolidines gives synthetically useful N-H-1,3-oxazinanes. 1,3-Oxazinanes are useful building blocks, which can be converted to N-H-1,3-aminoalcohols in a subsequent step.
C.-Z. Yao, Z.-F. Xiao, X.-S. Ning, J. Liu, X.-W. Zhang, Y.-B. Kang, Org. Lett., 2014, 16, 5824-5826.
The electrochemically induced catalytic multicomponent reaction of cyclic 1,3-diketones, aldehydes and malononitrile in alcoholic solvents results in the formation of substituted 5,6,7,8-tetrahydro-4H-chromenes in excellent yields.
M. N. Elinson, A. S. Dorofeev, S. K. Feducovich, S. V. Gorbunov, R. F. Nasybullin, F. M. Miloserdov, G. I. Nikishin, Eur. J. Org. Chem., 2006, 4335-4339.
A nickel-catalyzed cycloaddition of aziridines with isocyanates proceeded smoothly to give iminooxazolidine derivatives in good yields. A longer reaction time allowed the isomerization of the iminooxazolidine to the corresponding imidazolidinone derivatives.
T. Munegumi, I. Azumaya, T. Kato, H. Masu, S. Saito, Org. Lett., 2006, 8, 379-382.
Stereocontrolled Construction of O-Heterocycles
Asymmetric Hetero-Diels-Alder Reactions
O-Heterocyclic Construction by Alkene Metathesis
Stereoselective Construction of Oxygen Heterocycles