Aminocarbonyl complex

Alkoxides and amines also attack coordinated carbon monoxide to give alkoxycarbonyl and aminocarbonyl complexes, respectively (Equations 11.5 and 11.6). Stable complexes of both types have been isolated and thoroughly characterized. Less stable alkoxycarbonyl and carbamoyl complexes are intermediates in a number of synthetically important carbo-nylation processes discussed in Chapters 17 and 19. 

Nucleophilic attack on unsaturated u-bound ligands, such as acyl groups, is faster than attack on saturated alkyl ligands. Because the metal-bound carbon of these ligands can possess a partial negative charge, acyl, alkoxycarbonyl, and aminocarbonyl complexes... 

Ketimines are reduced to amines very easily by catalytic hydrogenation, by complex hydrides and by formic acid. They are intermediates in reductive amination of ketones (p. 134). An example of the reduction of a ketimine is conversion of 3-aminocarbonyl-2,3-diphenylazirine to the corresponding aziridine by sodium borohydride (yield 73%), by potassium borohydride (yield 71%) and by sodium bis (2-methoxyethoxy) aluminum hydride (yield 71%) [939]. 

The synthesis of aromatic primary amides through aminocarbonylation of aryl halides with ammonia is not well documented due to the technical difficulty in using gaseous ammonia. To resolve this problem, methods using ammonia equivalents such as hexamethyldisilazane (HMDS), " formamides, and a titanium-nitrogen complex have been developed. 

Since formamide is a weak nucleophile, the use of imidazole or 4-dimethylaminopyridine (DMAP) is necessary for acyl transfer to formamide via an activated amide (imidazolide) or acylpyridinium ion. As Scheme 22 illustrates, the reaction starts with the oxidative addition of aryl bromide 152 to Pd(0) species, followed by CO insertion to form acyl-Pd complex 154. Imidazole receives the aroyl group to form imidazolide 155 and liberates HPdBr species. Then, imidazolide 155 reacts with formamide to form imide 156. Finally, decarbonylation of imide 156 gives amide 157. In fact, the formations of imidazolide intermediate 155 and imide 156 as well as the subsequent slow transformation of imide 156 to amide 157 by releasing CO were observed. This mechanism can accommodate the CO pressure variations observed during the first few hours of aminocarbonylation. When the reaction temperature (120 °C) was reached, a fast drop of pressure occurred. This corresponds to the formation of the intermediary imide 156. Then, the increase of pressure after 3 h of reaction was observed. This phenomenon corresponds to the release of CO from imide 156 to form amide 157. ... 

The aminocarbonylation of alkynes has been less explored as compared to that of alkenyl and (hetero)aryl halides. Nevertheless, several noteworthy applications of this reaction have been reported, including the syntheses of 2-ynamides, chiral 2-carbamoyl-7r-allylic tungsten complexes, angular triquinanes, 2-(carbamoylmethylene)tetrahydrofurans, alle-nyl amides, and others. ... 

Aminocarbonylation has been combined with the Pauson-Khand reaction to construct fused tricyclic alkaloid skeletons (see 00154). The tandem aminocarbonylation/Pauson-Khand reaction of haloalkynes with a chiral allylic amine promoted by Co2(CO)8 gave angular triquinanes as exemplified in Scheme 25. Thus, the reaction of l-chloro-2-phenylethyne 175 with Co2(CO)8 at 0°C gave alkyne-dicobalt complex 176, which was converted to enoyl-dicobalt complex 177 upon warming to 25 °C. The reaction of enoyl-dicobalt complex 177 with cyclopente-nylmethyl(l-phenylethyl)amine 179 yielded Pauson-Khand reaction product, angular triquinane 180, via A -allylic aminocarbonylated alkyne-dicobalt complex 178 (Scheme 25). ... 

Carbonylation reactions with microwave irradiation have been investigated in connection with solid-state combinatorial chemistry.Since reactions requiring gaseous reagents cannot use microwave irradiation, metal carbonyl complexes, such as Mo(CO)6, Cr(CO)6, W(CO)6, and Co2(CO)8 have been employed as source of carbon monoxide. " Examples of aminocarbonylation performed with microwave irradiation are presented in Section 11.15.4.3 (vide supra). 

As stated above, aliphatic amines are potent ligands for electrophilic transition metals and are efficient catalyst poisons in attempted alkene animation reactions. However, tosylation of the basic amino group greatly reduces its complexing ability, yet does not compromise its ability to nucleophilically attack complexed alkenes. Thus, a variety of alkenic tosamides efficiently cyclized under palladium(II) catalysis producing N-tosylenamines in excellent yield (equations 17 and 18).32 Again, this alkene amination proceeded through an unstable a-alkylpalladium(II) species, which could be intercepted by carbon monoxide, to result in an overall aminocarbonylation of alkenes. With ureas of 3-hydroxy-4-pentenyl-amines (Scheme 7), this palladium-catalyzed process was quite efficient but it was somewhat less so with... 

Grignard additions, 9, 59, 9, 64 indium-mediated allylation, 9, 687 in nickel complexes, 8, 150 ruthenium carbonyl reactions, 7, 142 ruthenium half-sandwiches, 6, 478 and selenium electrophiles, 9, W11 4( > 2 in vanadocene reactions, 5, 39 Nitrites, with trinuclear Os clusters, 6, 733 Nitroalkenes, Grignard additions, 9, 59-60 Nitroarenes, and Grignard reactivity, 9, 70 Nitrobenzenes, reductive aminocarbonylation, 11, 543... 

A wide variety of RCCo3(CO)9 complexes may be prepared (R = H, halogen, alkyl, aryl, alkenyl, acyl, alkoxycarbonyl, aminocarbonyl, triorganosilyl, dialkyl phosphino, alkoxy, dialkylamino, etc.), either by direct reactions of octa-carbonyl dicobalt with organic tri- and dihalides or by acid-induced reactions of... 

The relative stereochemistry of the newly formed stereogenic centers attained in the aminometa-lation reaction of 1,2-disubstituted alkenes is lost if the / -aminoalkylpalladium complex is allowed to undergo /J-hydride elimination to give enamines, or if a successive reduction step is performed, unless a stereocenter is initially present in the alkene or in the amine. However, the C —Pd bond can be functionalized to achieve overall oxyamination, diamination, aziridination, aminocarbonylation, and carboamination reactions13,14. 

Vinyl bromides are directly aminocarbonylated by nickel carbonyl and amines. Very similarly, Rh (CO)i6 and BU4NCI as cat yst convert allylphosphates to. -y-unsaturated amides via rr-allylrhodium complexes (equation 43). Although palladium(O) complexes are more reactive than rhodium(I) complexes, palladium(O) complexes undergo side reactions, like reductive elimination in the presence of carbon monoxide, and direct nucleophilic attack by amines. 

In the presence of a nickel catalyst, aroyl-, alkanoyl, and aminocarbonyl-stannanes add to alkynes to give (3-acylvinylstannanes (Scheme 5.7.12). " Compared with other nickel-catalyzed carbostannylations of alkynes, the regioselectivity of the acylstannylation is not sufficient. The aminocarbonylstannylation of alkynes is also catalyzed by a rhodium complex. ... 

It is well recognized fhat aldimines are less reactive than aldehydes toward nucleophilic addition. In the presence of a catalytic amount of Yb(OTf)3, however, silyl enolates react with aldimines exclusively to afford / -aminocarbonyl compounds in high yield, even when aldehydes are present (Scheme 10.74) [209]. Selective formation of aldimine-Yb(OTf)3 complexes rather than aldehyde-Yb(OTf)3 complexes is attributable to fhe inverted reactivity. Polyallylscandium trifylamide ditriflate (PA-Sc-TAD), a polymer-supported Sc catalyst, also has high aldimine-selectivity. 

Gabriele et al. reported that the 2-oxazolidinones 462 were synthesized by the palladium-catalyzed oxidative carbonylation of the 2-amino- 1-alkanols 461 (Scheme 144).206 The aminocarbonyl palladium complex 463 is formed as an intermediate, and subsequent ring closure gives 462. 

This cyclization process provides a convenient route to complexes of ma-crocyclic ligands containing three or more nitrogen donor atoms. The template cation is an appropriate metal ion such as Ni(II) or Cu(ll). The reactants could be a dicarbonyl compound and an a,w-bis primary amine to form a cyclic bis Schiff base or an w-aminocarbonyl compound could be cyclized internally to form a cyclic mono Schiff base (Busch, 1967 Curtis, 1967). In a few cases, more than two Schiff bases were formed in the cyclization step. 

When the complex is treated with organic halides or acyl halides, dimethyl-aminocarbonylation proceeds smoothly. For example, reaction with benzyl bromide gave N,N-dimethylphenylacetamide in 64.5 %.96L... 

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