Amidation transition metal catalyzed

The last method for the preparation of 2-quinolones described in this chapter relies on a intramolecular Heck cyclization starting from heteroaryl-amides (Table 2) [57]. These are synthesized either from commercially available pyrrole- and thiophene-2-carboxylic acids (a, Table 2) or thiophene-and furan-3-carboxylic acids (b, Table 2) in three steps. The Heck cyclization is conventionally performed with W,Ar-dimethylacetamide (DMA) as solvent, KOAc as base and Pd(PPh3)4 as catalyst for 24 h at 120 °C resulting in the coupled products in 56-89% yields. As discussed in Sect. 3.4, transition metal-catalyzed reactions often benefit from microwave irradiation [58-61], and so is the case also for this intramolecular reaction. In fact, derivatives with an aryl iodide were successfully coupled by conventional methods, whereas the heteroarylbromides 18 and 19, shown in Table 2, could only be coupled in satisfying yields by using MAOS (Table 2). 

The insertion of unsaturated molecules into metal-carbon bonds is a critically important step in many transition-metal catalyzed organic transformations. The difference in insertion propensity of carbon-carbon and carbon-nitrogen multiple bonds can be attributed to the coordination characteristics of the respective molecules. The difficulty in achieving a to it isomerization may be the reason for the paucity of imine insertions. The synthesis of amides by the insertion of imines into palladium(II)-acyl bonds is the first direct observation of the insertion of imines into bonds between transition metals and carbon (see Scheme 7). The alternating copolymerization of imines with carbon monoxide (in which the insertion of the imine into palladium-acyl bonds would be the key step in the chain growth sequence), if successful, should constitute a new procedure for the synthesis of polypeptides (see Scheme 7).348... 

N-Acyl-a-amino acids are important compounds in both chemistry and biology. They are easily obtained in a transition metal-catalyzed, three-component domino reaction of an aldehyde, an amide, and CO. Whereas cobalt was mainly used for this process, Beller and coworkers [159] have recently shown that palladium has a... 

The transition metal-catalyzed C-H insertion reaction of carbenes to organic compounds is a well-established synthetic method, as shown in the first two sections in this chapter. However, nitrene C-H insertion, the corresponding reaction of carbene analog, is much less known. In the past decade, considerable advances have been made in the development of this chemistry into a generally useful C-H amination process by using improved catalysts and protocols, in which readily available amines or amides are used as the starting substrates. Moreover,... 

Numerous useful transition metal-catalyzed reactions of organic halides are now known. Practical syntheses of esters, acids, amides, aldehydes, olefins, ketones, and acetylenes have been described. In many instances the metal-catalyzed reactions are superior to more conventional, purely organic routes to the same compounds. 

Directed remote metalation (DreM) of biaryl amides and O-carbamates, conceptually based on the complex-induced proximity effect (CIPE) [15] provides, especially in view of their link to transition metal-catalyzed cross coupling regimens [16], general and versatile routes to fluorenones (16 —> 15, Scheme 4) [5,17] and biaryl amides (16 —> 17) [18] whose features are overriding Friedel-Crafts reactivity and yield enhancement in comparison to Suzuki-Miyaura coupling routes for highly hindered biaryls, respectively. Additional features of the O-carbamate DreM result is potential further DoM of 17 with appropriate phenol protection and cyclization to dibenzopyranones [18]. 

The transition metal catalyzed synthesis of arylamines by the reaction of aryl halides or tri-flates with primary or secondary amines has become a valuable synthetic tool for many applications. This process forms monoalkyl or dialkyl anilines, mixed diarylamines or mixed triarylamines, as well as N-arylimines, carbamates, hydrazones, amides, and tosylamides. The mechanism of the process involves several new organometallic reactions. For example, the C-N bond is formed by reductive elimination of amine, and the metal amido complexes that undergo reductive elimination are formed in the catalytic cycle in some cases by N-H activation. Side products are formed by / -hydrogen elimination from amides, examples of which have recently been observed directly. An overview that covers the development of synthetic methods to form arylamines by this palladium-catalyzed chemistry is presented. In addition to the synthetic information, a description of the pertinent mechanistic data on the overall catalytic cycle, on each elementary reaction that comprises the catalytic cycle, and on competing side reactions is presented. The review covers manuscripts that appeared in press before June 1, 2001. This chapter is based on a review covering the literature up to September 1, 1999. However, roughly one-hundred papers on this topic have appeared since that time, requiring an updated review. 

Alkenes with a variety of substituents such as acetal, amine, amide, carbamate, ester, ether, isocyanate, ketone, oxirane, and snlfide can be hydrosilated, usually without affecting the ftinctional group. However, this is not always fine for example, allyl chloride gives a considerable amount of the reduction product (see equation 26). Table 4 lists representative examples of hydrosilation. It is not so remarkable in the case of radical hydrosilation, but reactivity is high for hydrosUane, which has electronegative group in the case of transition metal catalyzed hydrosilation. 

Little is known about transition metal catalyzed epoxidation of simple allylic amides. The easily removable trichloroacetyl group is suitable as /V-substituent in the molybdenum-catalyzed epoxidation of (Z)-allylic systems with rm-butyl hydroperoxide, which produces the. sv -com-pound with appreciable selectivity21. 

There are interesting transition metal-catalyzed-reactions that lead to aryl amides. The use of POCI3 and DMF, with a palladium catalyst, converts aryl iodides to benzamides. A palladium-catalyzed reaction of aryl hahdes and for-mamide leads to benzamide derivatives. Carbonylation is another method that generates amides. When an aryl iodide was treated with a secondary amine and Mo(CO)e, in the presence of 3 equivalents of DBU, 10% Pd(OAc)2, with micro-wave irradiation at 100°C, the corresponding benzamide was obtained. 

There are transition-metal catalyzed addition reaction of alkyl units to alkenes, often proceeding with metal hydride elimination to form an alkene. An intramolecular cyclization reaction of an A-pyrrolidino amide alkene was reported using an iridium catalyst for addition of the carbon ot to nitrogen to the alkene unit. OS I, 229 IV, 665 VII, 479. 

Following the pioneering work of Breslow and Gellman, transition metal-catalyzed inter- and intramolecular C-H functionalizations (aminations or amidations) have advanced tremendously in recent decades/ """ Characteristic examples are Rh-catalyzed insertions into allylic or benzylic C-H bonds [Eq. (6.134)] and the transformation of carbamates to oxazolidi-nones [Eq. (6.135)] ... 

Recently, transition-metal-catalyzed reaction of iminoiodinanes 731 has been focused as a method of nitrogen transferring (Scheme 226). The iminoiodinanes 731 are readily synthesized from sulfor-amides or carbamates 730 by treatment with Phl-(OAc)2. The reaction of 731 with a transition-metal catalyst M produces the metal nitrenoid 732. The... 

The synthesis of carboxylate-substituted imidazoline derivatives has previously been accomplished by the condensation of presynthesized 1,2-diamines with amides, or through the transition metal catalyzed aldol-type reaction between isocyanates and imines (4,5). We have recently communicated an alternative palladium catalyzed route to synthesize a new class of imidazoline carboxylates, utilizing acid chloride, imines and carbon monoxide as starting materials (see Table 1)... 

The products are versatile auxiliaries not only for enantioselective deprotonation and elimination (Section C.), but are also valuable chiral ligands for complex hydrides in the enantioselective reduction of ketones (Section D.1.4.5.)- They are also applied in enolate reactions (Section D.l.5.2.1., D.1.5.2.4.). transition-metal-catalyzed Michael additions (Section D.l.5.8.), 1,3-dipolar cycloadditions (Section D.l.6.1.2.1.), and additions ofGrignard reagents (Section D.l.3.1.4.2.5.). (5 )-2-(Phenylaminomethyl)pyrrolidine has found most application and is also commercially available. Several methods exist for the preparation of such compounds. Two typical procedures for the synthesis of (.S)-2-(l-pyrrolidinylmcthyl)pyrrolidine are presented here. The methodology can be readily extended to other amides and alkylamino derivatives of proline. 

Imidoiodanes and especially A-tosyliminoiodanes, ArINTs (Section 2.1.12.4), have found broad synthetic application as useful nitrene precursors in transition metal catalyzed aziridination of aUcenes and amidation of various organic substrates [584, 761]. Mansuy and coworkers in 1984 first reported the aziridination of alkenes with tosyliminoiodane PhINTs in the presence of iron- or manganese-porphyrins [762]. This reaction has a mechanism similar to the metal-catalyzed oxygen atom transfer reactions of iodosylbenzene (Section 3.1.20) and involves a metal-nitrene complex as the intermediate. 

IV-Tosyliminoiodanes, ArINTs, have found synthetic application as useful nitrene precursors in transition metal catalyzed amidation of saturated C—H bonds in various organic substrates. Breslow and coworkers have developed the regioselective amidation of steroidal derivatives catalyzed by metalloporphyrins [690,691]. Specifically, the aromatic steroid equilenin acetate 657 undergoes regioselective and stereoselective amidation catalyzed by a manganese porphyrin using PhINTs as the nitrene donor (Scheme 3.261) [690],... 

The preparation of cyclopentenone from the three-component transition-metal-catalyzed [2+2+1] cycloaddition of an alkyne, alkene, and carbon monoxide in the presence of a stoichiometric amount of Co2(CO)g was first reported by Khand et al. in 1973 (Scheme 2-l2)P This reaction is attractive for organic synthesis as it tolerates a wide variety of functionalities including esters, ethers, tertiary amines, amides, and alcohols. 

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