A ruthenium catalyst bearing a fused π-conjugated imidazo[1,2-a][1,8]naphthyridine-based abnormal N-heterocyclic carbene ligand enables a selective oxidation of C═C bonds in a broad range of substrate to aldehydes and C≡C bonds to α-diketones in an EtOAc/CH3CN/H2O solvent mixture at room temperature.
P. Daw, R. Petakamsetty, A. Sarbajna, S. Laha, R. Ramapanicker, J. K. Bera, J. Am. Chem. Soc., 2014, 136, 13987-13990.
Osmium tetroxide has been microencapsulated in a polyurea matrix. These microcapsules have been effectively used as recyclable catalysts in the dihydroxylation and the oxidative cleavage of olefins.
S. V. Ley, C. Ramarao, A.-L. Lee, N. Ostergaard, S. C. Smith, I. M. Shirley, Org. Lett., 2003, 5, 185-187.
Specific oxidation protocols have been developed for the cleavage of styrenes, aliphatic olefins, and terminal aliphatic olefins to carbonyl compounds with ruthenium trichloride as catalyst. Olefins that are not fully substituted are converted to aldehydes rather than carboxylic acids.
D. Yang, C. Zhang, J. Org. Chem., 2001, 66, 4814-4818.
A catalytic amount of a composite material, RuO2/BaTi4O9, in combination with NaIO4 in EtOAc-H2O has been shown to efficiently cleave alkenes, affording ketones, aldehydes and/or carboxylic acids in high yields.
H. Okumoto, K. Ohtsuko, S. Banjoya, Synlett, 2007, 3201-3205.
A high-yielding, asymmetric synthesis of novel 4-formyl-1-(2- and 3-haloalkyl)azetidin-2-ones was developed as valuable starting materials for the synthesis of different enantiomerically enriched bicyclic azetidin-2-ones, such as piperazine, morpholine, and 1,4-diazepane annulated β-lactam derivatives.
W. Van Brabandt, M. Vanwalleghem, M. D'hooghe, N. De Kimpe, J. Org. Chem., 2006, 71, 7083-7086.
An improved protocol for the RuO4-catalyzed syn-dihydroxylation uses only 0.5 mol% catalyst under acidic conditions. Various olefins can be hydroxylated in good to excellent yields with only minor formation of side products.
B. Plietker, M. Niggemann, Org. Lett., 2003, 3353-3356.
LiBr is an efficient catalyst for the dihydroxylation of alkenes to afford either syn or anti diols with excellent diastereoselectivity depending upon the use of NaIO4 or PhI(OAc)2 as the oxidants.
L. Emmanuvel, T. M. A. Shaikh, A. Sudalai, Org. Lett., 2005, 7, 5071-5074.
Grubbs' 2nd generation metathesis catalyst can be used in tandem olefin metathesis/oxidation protocols. These ruthenium-catalyzed processes provide access to cis-diols or α-hydroxy ketones from simple olefinic starting materials.
A. A. Scholte, M. H. An, M. L. Snapper, Org. Lett., 2006, 8, 4759-4762.
A new one-pot method is described for the removal of O- and N-allyl protecting groups under oxidative conditions at near neutral pH. The allyl group undergoes hydroxylation and subsequent periodate scission of the vicinal diol. Repetition of this reaction sequence on the enole tautomer of the aldehyde intermediate releases the deprotected functional group.
P. I. Kitov, D. R. Bundle, Org. Lett., 2004, 3, 2835-2838.
A catalytic, asymmetric conjugate addition of carbamates to enoyl systems provides a highly enantioselective two-step access to N-protected β-amino acids.
C. Palomo, M. Oiarbide, R. Halder, M. Kelso, E. Gómez-Bengoa, J. García, J. Am. Chem. Soc., 2004, 126, 9188-9189.
A highly enantioselective and catalytic vinylation of aldehydes leads to allylic alcohols that are then transformed to the allylic amines via Overman's [3,3]-sigmatropic rearrangement of imidates. Oxidative cleavage of the allylic amines furnishes amino acids in good yields and excellent ee's. The scope and utility of this method are demonstrated by the synthesis of challenging allylic amines and their subsequent transformation to valuable nonproteinogenic amino acids, including both D and L configured (1-adamantyl)glycine.
Y. K. Chen. A. E. Lurain, P. J. Walsh, J. Am. Chem. Soc., 2002, 124, 12225-12231.
The combination of sodium periodate, potassium iodide, and sodium azide is an efficient, simple, and inexpensive reagent system for azidoiodination of alkenes. The regiospecific 1,2-azidoiodination proceeds in an anti-Markovnikov fashion to produce β-iodoazides in excellent yields.
P. V. Chouthaiwale, P. U. Karabal, G. Suryavanshi, A. Sudalai, Synthesis, 2010, 3879-3882.
Deactivated arenes were mono- or diiodinated with strong electrophilic I+ reagents, which were prepared from NaIO4 and either I2 or KI in concentrated sulfuric acid, using either a ‘direct’ or an ‘inverse’ method of aromatic iodination to give mono- or diiodinated pure products in good yields.
L. Kraszkiewicz, M. Sosnowski, L. Skulski, Synthesis, 2006, 1195-1199.
A novel, high-yielding method for sulfation of alcohols proceeds via sulfite- and sulfate diester intermediates. Sulfite diesters serve as versatile sulfate monoester precursors, that allow interesting transformations.
M. Huibers, I. Manuzi, F. P. J. T. Rutjes, F. L. van Delft, J. Org. Chem., 2006, 71, 7473-7476.
The reaction of alkenes with sodium arene sulfinates in the presence of potassium iodide and sodium periodate and a catalytic amount of acetic acid provides vinyl sulfones at room temperature. The products are formed in high yields within hours.
B. Das, M. Lingaiah, K. Damodar, N. Bhunia, Synthesis, 2011, 2941-2644.
Arylboronic acids and aryl trifluoroborates are synthesized in a one-pot sequence by Ir-catalyzed borylation of arenes. To prepare the arylboronic acids, the Ir-catalyzed borylation is followed by oxidative cleavage of the pinacol boronates with NaIO4. To prepare the aryltrifluoroborate, the Ir-catalyzed borylation is followed by displacement of pinacol by KHF2.
J. M. Murphy, C. C. Tzschucke, J. F. Hartwig, Org. Lett., 2007, 9, 757-760.