Of special interest are the catalytic conditions developed by Rosini et al. Among the C2 symmetric diols which were used instead of DET, mention might also be made of diol 45, as prepared by Imamoto et al. This gave moderate ee-values in the preparation of some sulfoxides, unless some subsequent kinetic resolution was allowed.
Higher ee-values but lower yields could be achieved by combining this with a kinetic resolution [66b]; chiral diphenols 47 , 48  and 49  have been used instead of binol itself. Compound 50 is a good precursor of a variety of sulfoxides by a displacement reaction of CH2P O OEt 2 by organometallics.
The catalytic activity was good 1 mol. In this respect, an interesting mechanistic study has been conducted and a peroxo complex 52 isolated. Complex 54 was transformed, according to a procedure described by Belokon et al. Presumably, UHP cleanly transforms complex 55 into the active peroxo complex In the presence of water, 56 is in equilibrium with the less-stereoselective hydroperoxo hydroxo titanium species.
The family of Salen manganese III provided some active enantioselective catalysts. For example, Jacobsen et al. Later, Katsuki et al. Mukaiyama et al. Skarzewski et al. Katsuki et al. The Bolm procedure, when applied to the asymmetric synthesis of aryl ben- Scheme 1.
The reaction was subsequently optimized for large-scale production [83b]. Salan—oxovanadium complexes were also shown to be excellent catalysts in asymmetric sulfoxidations using hydrogen peroxide as oxidant .
Recently, Yamamoto and colleagues investigated the potential of a chiral Mo complex of a bis-hydroxamic acid 65 Scheme 1. The best results were obtained with trityl hydroperoxide as oxidant at 0 8C in dichloromethane. The catalyst 2 mol. Higher ee-values may be obtained by combining with a kinetic resolution through overoxidation to sulfone, albeit at the expense of the yield. Fontecave and colleagues studied the binuclear complex 66 Scheme 1. A successful approach was developed by Bolm et al.
This protocol was improved by the introduction of an additive 10 mol. In some cases, kinetic resolution was also observed when the sulfone was produced.
A mechanistic study of the iron-catalyzed oxidation of thioethers by iodosylarenes was recently reported by Bryliakov and Talsi [90b]. Iron complexes such as 68 and analogues have been screened, and are very active 0.
The enantioselectivity was modest, after which the authors examined the binol-derived complex 69b . The oxidation was run in methanol with 2 mol. Some kinetic resolution was apparent if there was any overoxidation to sulfones.
Heterogeneous titanium complexes derived from multitopic binol ligands are excellent and robust catalysts of sulfoxidation [91c]. Under optimized conditions 2 mol. Chiral hydroperoxides such as 73 represent another class of reagent which has provided higher enantiomeric excesses Scheme 1. Hydroperoxides such as 74 were also used as excellent chiral oxidants, with Ti Oi-Pr 4 as promoter . The enantioselectivity was modest at low conversion, and increased with a subsequent kinetic resolution.
These reagents are derived from camphor for a review, see Ref. One crucial structural factor here is the presence of a gem-dihalo system in the vicinity of the oxaziridine ring as in 76—77, Scheme 1.
Typically, the reaction was carried out in CCl4 at room temperature. Bulman Page et al. In principle, this procedure should give rise to a catalytic version by respect to 80, with the in-situ generation of oxaziridines. The imine 81 could be quantitatively recovered, however. A family of N-phosphinooxaziridines synthesized by Jennings et al.
The oxaziridine 82 and its oxaziridinium salt 83 see Scheme 1. The imine deriving from 86 could be recovered and recycled. Bromine oxidation of Scheme 1. Another problem is the competitive oxidation of sulfoxide into sulfone, which leads to a decrease in yield, although the ee-values may be increased by kinetic resolution for some additional examples to those mentioned above, see Refs. It is remarkable that, when required, the large-scale asymmetric syntheses of sulfoxides has been realized in either stoichiometric or catalytic mode.
Harrison, J. Kenyon, H. Phillips, J. Morrison Ed. Carreno, Chem. Fernandez, N. Khiar, Chem. Andersen, in: S. Patai, Z. Rappoport, C. Stirling Eds. Drabowicz, P. Kielbasinski, M. Mikolajczyk, in: Z. Pellissier, Tetrahedron , 62, — Legros, J. Delhi, C. Bolm, Adv. Andersen, Tetrahedron. Andersen, W. Papanikolaou, J. Foley, R. Perkins, J. Mislow, M. Green, P.
Laur, J. Melillo, T. Simmons, A. Ternay, Jr. Bickart, M. Axelrod, J. Jacobus, K. Mislow, J. Field, C. Clark, Org. Syntheses, Coll. IV, , Mioskowski, G. Klunder, K. Sharpless, J. Axelrod, C. Bickart, J. Jacobus, M. Green, K. Pyne, A. Hajipour, K. Prabakaran, Tetrahedron Lett. Cherkaoui, J. Nicoud, New J. Andersen, B. Bujnicki, J. Drabowicz, M. Mikolaczyk, J. Whitesell, M. Wong, J. Ridley, M. Smal, Chem. Smal, Aust. Llera, I. Fernandez, F. Alcudia, Tetrahedron Lett. Khiar, J. Lhera, F.
Alcudia, J. Khiar, I. Khiar, A. Roca, A. Benabra, A. Esparter, F. Nowczyk, C. Alayra, V. Reboul, P. Metzner, M. Averbuch-Pouchot, J. Barcells, G. Ujaque, I. Khiar, F. Maseras, J. Maseras, Adv. Shibata, M. Matsunaga, M. Nakagawa, T. Fukuzumi, S. Nakamura, T. If the reaction of potassium with liquid ammonia slows down before all the potassium is consumed, an additional pinch of ferric nitrate hydrate is added.
Discussion 3-Acetyloxindole has been made by condensing ethyl acetate with oxindole in the presence of sodium ethoxide3 and by heating N-acetyloxindole with sodium amide in xylene. This principle involves the creation of an intermediate species that is of the benzyne type and has a nucleophilic center located so that it can add, intramolecularly, to the "triple bond" of the benzyne structure.
Trimethylorthoformate is not suitable for this preparation because of side-product formation. Diethyl oxalate was purchased from Merck and Company, Inc. However, this complex is less active and is difficult to store. Dimethyl sulfoxide DMSO prevents precipitation of intermediate salts, which can also be achieved by using a larger volume of dimethylformamide DMF ca. At elevated temperatures e.
The product gave a bright-red spot at Rf 0. Crude 4-nitroindole can also be purified by recrystallization from methanol, ethanol, or acetonitrile giving brownish-yellow crystals, mpC.
However, 4-benzyloxyindole was first prepared relatively recently in modest overall yield by the Reissert method, which involves condensation of 6-benzyloxy-2nitrotoluene with ethyl oxalate, reductive cyclization to the indolecarboxylate, hydrolysis to the acid, and decarboxylation. This efficient, two-step procedure8,9 illustrates a general, simple, and convenient process for preparing a variety of indoles substituted in the carbocyclic ring.
Since many of these examples served to determine the scope of this method, the yields in most cases have not been optimized.
In many cases, the starting materials are readily available or can be easily prepared. The present procedure, however, has two useful elements of flexibility: it produces both 3-alkyland 3-acylindoles from a single precursor, and it tolerates the presence of a wide variety of substituents.
The pivotal step in this sequence is an electrophilic substitution on indole. Smith, Neil K. Journal of the American Chemical Society , 20 , Jie S. Teuthorn, Makhluf J. Haddadin, Mark J. Kurth, and Dean J. The Journal of Organic Chemistry , 82 20 , Organic Letters , 19 19 , Organic Letters , 19 7 , Myles W. Smith, Zhiyao Zhou, Alison X. Gao, Takuya Shimbayashi, and Scott A.
Organic Letters , 19 5 , Eric S. Andreansky and Simon B. Organic Letters , 18 24 , Artur K. Mailyan, John A. Eickhoff, Anastasiia S. Chemical Reviews , 7 , Journal of the American Chemical Society , 12 , Morrill, Joel M. Smith, and Neil K. Journal of the American Chemical Society , 4 , Organic Letters , 17 22 ,Simmons, A. Perio, S. Kagan et al. The procedure labeled herein is fairly general for indoles, and since 2-methylthio-1,3-dithianes are then available, it should prove versatile. Marsch, J. Garnish, G. Gao, Takuya Shimbayashi, and Miles A. Yanai, T. Morrison Ed. Are of the American Chemical Programmer22.
Rappoport, C. Cherkaoui, J. Boal, and Neil K. Although this use is widespread in the United States, the U. Rudolph, N.
Modena, S. Benjamin D. Maseras, Adv. Bickart, M. The procedure described herein is fairly general for indoles, and since 2-methylthio-1,3-dithianes are readily available, it should prove versatile. Fernandez, N.
Sasaki, T. Samuel, L.
TBZ did not inhibit peptide synthesis in a cell-free protein-synthesizing system from Rhizoctonia solani. Fukuzumi, S. Detailed experimental procedures and compound characterization data. Organic Letters , 14 17 ,