Synthesis and Reactivity of Ortho-Palladated Phenylacetamides. Intramolecular C−N vs C−O Reductive Coupling after CO or XyNC Insertion into the Pd−C Bond. Synthesis of Isoquinoline- and Isocoumarin-Based Heterocycles

Abstract

Aryl palladium complexes [Pd{C 6 H 4 CH 2 C(O)NRR 0 -2}I(N ∧ N)] (N ∧ N = N,N,N 0 ,N 0 -tetramethylethylenediamine = tmeda, NRR 0 = NH 2 (1a), NHMe (1b), NMe 2 (1c); N ∧ N = 4,4 0 -di-tert-butyl-2,2 0 -bipyridyl (dbbpy), NRR 0 = NHMe (1b 0 )) are prepared by oxidative addition of the corresponding 2-(2-iodophenyl)acetamide to "Pd(dba) 2 " ([Pd 2 (dba) 3 ] 3 dba; dba = dibenzylideneacetone) in the presence of the N ∧ N chelating ligand. Cationic cyclometalated derivatives [are obtained by reacting the appropriate complex 1 with AgOTf. The reaction of 2b 0 with PPh 3 affords [Pd{C 6 H 4 CH 2 C(O)NHMe-2}(dbbpy)(PPh 3 )]OTf (3b 0 ). Neutral amidate complexes of the type [Pd{κ 2 C,N-C 6 H 4 CH 2 C(O)NR-2}(N ∧ N)] (N ∧ N = tmeda, R = H (4a), Me (4b); N ∧ N = dbbpy, R = Me (4b 0 )) are obtained upon deprotonation of the corresponding complex 1 with KO t Bu. The complex [Pd{C 6 H 4 CH 2 C(O)NHMe-2}{CH(CN) 2 }(dbbpy)] (5b 0 ) has been prepared by reacting 4b 0 with malononitrile. Acyl derivatives [Pd{C(O)C 6 H 4 CH 2 C(O)NRR 0 -2}I(N ∧ N)] (N ∧ N = tmeda, NRR 0 = NH 2 (6a), NHMe (6b), NMe 2 (6c); N ∧ N = dbbpy, NRR 0 = NHMe (6b 0 )) have been prepared by reacting the corresponding complex 1 with CO at low temperature; when N ∧ N = tmeda, prolonged reaction times and high temperatures lead to Pd(0) and isoquinoline-1,3(2H,4H)-dione (7a), a 1:2 mixture of 2-methylisoquinoline-1,3(2H,4H)-dione (7b) and 3-(dimethylamino)-1H-2-benzopyran-1-one (8b), or 3-(methylamino)-1H-2-benzopyran-1-one (8c), respectively. Similar results are obtained from the reactions of 2a-c with CO under much milder conditions, while 2b 0 reacts with CO in acetone to give the isochroman-1-one derivative N,3,3-trimethyl-1-oxo-3,4-dihydro-1H-2-benzopyrane-4-carboxamide (9). While the reaction of 1b 0 with 1 equiv of XyNC (Xy = 2,6-dimethylphenyl) gives the iminoacyl complex [Pd{C(dNXy)-C 6 H 4 CH 2 C(O)NHMe-2}I(dbbpy)] (10b 0

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, 1 −C(O)Me, 1b,2 −CN, 1b −(CRR′) n NH 2 (n = 0−2), 3 −(CRR′)NHOH, 4 −CH 2 OEt, 5 −CHCHR, 1b,6 C(O)NHBu t , 7 OH, 8 −N PPh 3 , 9 −CH(SCH 2 ) 2 , −CH(SR) 2 , 10 −SR, 11 −NCNR, −NCS, 12 −NHC(O)NRR′, 13 −(CH 2 ) n C(O)NRR′ (n = 1, 2), 14 and −NHC(Me)CHC(O)Me. 15 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 6b, 10,12,13,16 or, after depalladation, new organic products.…”

Cyclopalladated complexes derived from benzamidoxime

“…The low energy of the CvNXy band in the iminobenzoyl fragment in 7 (1615 cm −1 ) must be attributed to its conjugation with the arene fragment, as has been observed in other iminobenzoyl complexes. 18 The ν(PdCl) bands have been assigned only tentatively because of the presence of some other weak bands in the same region. In the IR spectra of complexes 2 and 7 they appear in the range 282-298 cm −1 indicating the disposition of the chloro ligand is trans to the arene or the iminobenzoyl moiety, respectively, as confirmed by the crystal structures of 2a and 7.…”

Reactions of m-chloroperoxybenzoic acid with dimeric cyclopalladated complexes derived from 2-phenyl-2-oxazolines

“…Reactions at the C-Pd bond of cyclopalladated complexes (CPCs) [1][2][3][4][5] (e.g., phosphination [6][7][8][9][10], chlorination [11][12][13][14], iodination [15][16][17][18][19], bromination [15,16], acetoxylation [20][21][22][23][24][25] and other transformations [15,[26][27][28][29][30][31]) represent an attractive method for highly regioselective functionalization of organic compounds. These Pd-mediated transformations are gaining importance as a synthetic method, providing access to new organic and organometallic compounds not readily available by other methods.…”