Synthesis and Reactivity of Ortho-Palladated 3-Phenylpropanamides. Insertion of CO, XyNC, and Alkynes into the Pd–C Bond. Synthesis of Seven- and Nine-Membered Palladacycles and Benzazepine- and Benzazonine-Based Heterocycles

Abstract

Aryl palladium complexes [Pd{C 6 H 4 (CH 2 ) 2 C(O)-NRR′)-2}I(tmeda)] [NRR′ = NH 2 (1a), NHMe (1b), NMe 2 (1c); tmeda = N,N,N′,N′-tetramethylethylenediamine] are prepared by oxidative addition of the corresponding 3-(2iodophenyl)propanamides to "Pd(dba) 2 " ([Pd 2 (dba) 3 ]•dba; dba = dibenzylideneacetone) in the presence of tmeda. The cationic seven-membered palladacycles [Pd{κ 2 C,O-C 6 H 4 (CH 2 ) 2 C(O)-NRR′)-2}(tmeda)]TfO (2a−c) are obtained by reacting 1a−c with AgTfO. Neutral amidate complexes of the type [Pd{κ 2 C,N-C 6 H 4 (CH 2 ) 2 C(O)NR)-2}(tmeda)] [R = H (3a), Me (3b)] are obtained upon deprotonation of the amide function in 1a or 1b with KO t Bu. The reaction of 1a with CO at room temperature affords the stable acyl derivative [Pd{C(O)C 6 H 4 (CH 2 ) 2 C-(O)NH 2 -2}I(tmeda)] (4), while 2a gives Pd, (tmedaH)TfO, and 4,5-dihydro-2H-benzo[c]azepine-1,3-dione (5a). Compound 5a can also be obtained in high yield by treating the amidate complex 3a with CO, while a low yield of 2-methyl-4,5-dihydro-2Hbenzo[c]azepine-1,3-dione (5b) was obtained from 3b under the same conditions. Complexes 1a−c react with 3 equiv of XyNC to give trans-[Pd{C(NXy)C 6 H 4 (CH 2 ) 2 C(O)NRR′-2}I(CNXy) 2 ] [NRR′ = NH 2 (6a), NHMe (6b), NMe 2 (6c)]. By refluxing a CHCl 3 solution of 6a or 1a and XyNC in 1:1 molar ratio, mixtures of 1-(2,6-dimethylphenylimino)-1,2,4,5tetrahydrobenzo[c]azepin-3-one (7a) and 2-(2-cyanoethyl)-N-(2,6-dimethylphenyl)benzamide (8a) are obtained. Complexes 2a−c react with alkynes in 1:1 molar ratio to give nine-membered palladacycles of the type [Pd{κ 2 C,O-C(X) C(X)C 6 H 4 (CH 2 ) 2 C(O)NRR′-2}(tmeda)]TfO [NRR′ = NH 2 , X = Ph (9a), C 6 H 4 n Bu-4 (10a), C 6 H 4 Br-4 (11a), CO 2 Me (12a); NRR′ = NHMe, X = Ph (9b); NRR′ = NMe 2 , X = Ph (9c)]. The reaction of 2a with an excess of 3-hexyne gives the complex [Pd{η 3 -C 6 H 4 (C 4 Et 4 )(CH 2 ) 2 C(O)NH 2 }(tmeda)]TfO (13), containing a spirocyclic ligand coordinated to Pd through a η 3 -allylic bond. The derivatives 9a, 10a and 11a react with CO at 50 °C in CHCl 3 to give colloidal Pd, (tmedaH)TfO, and the corresponding 6,7-disubstituted 1,2-dihydro-4H-benzo[e]azonine-3,5-diones (14, 15, 16), which result from a CO insertion/C− N reductive coupling sequence.

Synthesis of Aryl-, Benzoyl-, and Iminobenzoyl-Palladium(II) Complexes Derived from N-Phenyl Formamide. Synthesis of a Homoleptic Ball-Shaped Tetranuclear Palladium Complex

“…During the past few years, we have been interested in the synthesis of ortho -functionalized aryl palladium complexes with the purpose of studying their reactivity toward unsaturated molecules. Following this idea, we have reported insertion reactions of CO, RNC, acetylenes, olefins, O 2 , nitriles, cyanamides, isothiocyanates, carbodiimines, or allenes as well as sequential insertion reactions of some of these reagents into the C–Pd bond of ortho -functionalized aryl palladium complexes containing the ortho -group −CHO, −C­(O)­Me, , −CN, −(CRR′) n NH 2 ( n = 0–2), −(CRR′)­NHOH, −CH 2 OEt, −CHCHR, , C­(O)­NHBu t , OH, −NPPh 3 , −CH­(SCH 2 ) 2 , −CH­(SR) 2 , −SR, −NCNR, −NCS, −NHC­(O)­NRR′, −(CH 2 ) n C­(O)­NRR′ ( n = 1, 2), and −NHC­(Me)­CHC­(O)­Me . Interestingly, the resulting complexes were not only the expected insertion products but frequently also the result of some process that produced new types of complexes ,,,, or, after depalladation, new organic products. − ,,, Related reactions have also been reported by other groups …”

Palladium-Mediated Functionalization of Benzofuran and Benzothiophene Cores

“…Unsaturated species, such as isocyanides, carbon monoxide, and alkenes, readily insert into the Pd–C bond of aryl-complexes to afford organometallic iminoacyl, acyl-, and alkyl-derivatives or organic compounds upon further decomposition. , The accepted mechanism of these insertion reactions into the Pd–C bond involves (1) coordination of the unsaturated molecule to the metal center and (2) migratory insertion of the aryl group to the coordinated ligand. , These organometallic intermediates can be stable enough to be isolated or evolve through a reductive elimination process to afford the corresponding organic derivatives. , …”

The Solid-State Structures of Cyclic NH Carboximides

“…In this way each molecule has two donor and two acceptor interactions and is involved in two R Four structures have been reported for eight-and nine-membered cyclic NH carboximides all of which, viz. 278 [234], 279 [235], 280 [235] and 281 [236] (Figure 80) exist as simple NH to CO hydrogen-bonded R…”

“…Four structures have been reported for eight-and nine-membered cyclic NH carboximides all of which, viz. 278 [234], 279 [235], 280 [235] and 281 [236] (Figure 80) exist as simple NH to CO hydrogen-bonded R 2 2 (8) dimers of pattern A. It is notable that between the closely similar compounds 279 and 280 the opposite imide CO is involved.…”