Reactions with C-, N-, O-, and

Base-catalyzed hydrogen exchange, 16, 1 Basicity and acidity of azoles, 41, 187 Behavior of monocyclic 1,2,4-triazines in reactions with C-, N-, O-, and S-nucleophiles, 46, 73 1-, 2-, and 3-Benzazepines, 17, 45 Benzisothiazoles, 14, 43 38, 105 Benzisoxazoles, 8, 277 29, 1 Benzoazines, reactivity with nucleophiles,... 

Behavior of Monocyclic 1,2,4-Triazines in Reactions with C-, N-, O-, and S-Nucleophiles... 

Over the last few years, the Ir-catalyzed allylic substitution has been investigated in several laboratories and was found to be well suited for applications in organic synthesis. Using this reaction, branched chiral allylic derivatives can be prepared with high selectivity from simple achiral monosubstituted allylic substrates (Scheme 11.1). The reaction has been carried out with C, N, O, and S nucleophiles. The very broad range of nucleophiles is impressive. Several reviews have appeared on the subject [1]. At present, the best catalysts are prepared from [Ir(cod)Cl]2 (cod, cycloocta-1,5-diene) [2, 3] or [Ir(dbcot)Cl]2 (dbcot, dibenzocyclooctatetraene) [4] and a chiral phosphoramidite by base-induced C-H activation. Reliable experimental procedures have been developed for the reaction [5]. 

The key-steps in many organocatalytic cycles are electrophile-nucleophile combinations. The reactions of carbocations and Michael acceptors with C, N, O, and P nucleophiles were carefully studied by Mayr, providing an empirical equation able to describe the reaction rates [4]. 

The formation and intramolecular dipolar cycloaddition of azomethine ylides formed by carbenoid reaction with C=N bonds has recently been studied by the authors group.84 Treatment of 2-(diazoace-tyl)benzaldehyde O-methyl oxime (176) with rhodium(II) octanoate in the presence of dimethyl acetylenedicarboxylate or N-phenylmaleimide produced cycloadducts 178 and 179, respectively. The cycloaddition was also carried out using p-quinone as the dipolarophile. The major product isolated corresponded to cycloadduct 180. The subsequent reaction of this material with excess acetic anhydride in pyridine afforded diacetate 181 in 67% overall yield from 176. The latter compound incorporates the basic dibenzofa, d -cyclohepten-5,10-imine skeleton found in MK-801,85 which is a selective ligand for brain cyclidine (PCP) receptors that has attracted considerable attention as a potent anticonvulsive and neuro-protective agent.86,87... 

In soil solutions the most important chemical elements that undergo redox reactions are C, N, O, S, Mn, and Fe. For contaminated soils the elements As, Se, Cr, Hg, and Pb could be added. Table 2.4 lists reduction half-reactions (most of which are heterogeneous) and their equilibrium constants at 298.15 K under 1 atm pressure for the six principal elements involved in soil redox phenomena. Although the reactions listed in the table are not full redox reactions, their equilibrium constants have thermodynamic significance and may he calculated with the help of Standard-State chemical potentials in the manner... 

The formation and intramolecular dipolar cycloaddition of azomethine ylides formed by carbenoid reaction with C-N double bonds has recently been studied by the author s group [66]. Treatment of 2-(diazoacetyl)benzaldehyde O-methyl oxime (118) with rhodium (II) octanoate in the presence of dimethyl acetylenedicarboxylate or iV-phenylmaleimide produced cycloadducts 120 and... 

Dipolar cycloadditions 6.12 + 6.13 —> 6.14, however, are a large group of [4 + 2] cycloadditions isoelectronic with the allyl anion+ alkene reaction. There is much evidence that these reactions are usually concerted cycloadditions. They have a conjugated system of three p orbitals with four electrons in the conjugated system, but the three atoms, X, Y, and Z in the dipole 6.12 and the two atoms A and B in the dipolarophile 6.13, are not restricted to carbon atoms. The range of possible structures is large, with X, Y, Z, A and B able to be almost any combination of C, N, O and S, and with a double 6.12 or, in those combinations that can support it, a triple bond 6.15 between two of them. 

Transition metal-tin bonds are the most common type of bonds after those with p-block elements, namely C, N, O, and halogens. The less common transition metal-tin bonds are associated with early transition metals, namely Ti, Zr, Flf, V, Ta, and Nb. A fundamental difficulty in this bond formation is the existence of energetically low-lying electron transfer reaction pathways from the tin to the early transition metal. An interesting approach to the synthesis of group 4 metal-tin bonds comprises the use of tripodal amido... 

Few efforts have been devoted to carbenoid reactions with C=N and C=O groups since the last two reviews covering this field were written. 

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