Roberto A. Rossi

Room-Temperature Photoinduced Direct C–H-Arylation via Base-Promoted Homolytic Aromatic Substitution

Conceptually different approach toward biaryl syntheses by photoinduced direct C-H arylation of benzene and thiophene in the presence of t-BuOK is reported. The reaction proceeds through photo- and base-promoted homolytic aromatic substitution. The o-, m- and p- substituted ArI, as well as the electron-donating and electron-withdrawing nature of the substituents were found be good to excellent substrates. Heteroaryl, ArBr, ArCl and double C-H arylation were successfully achieved.

Electron-Transfer-Mediated Synthesis of Phenanthridines by Intramolecular Arylation of Anions from N-(ortho-Halobenzyl)arylamines: Regiochemical and Mechanistic Analysis

The synthesis of a series of substituted phenanthridines by photostimulated C-C cyclization of anions from N-(ortho-halobenzyl)arylamines has been found to proceed in very good to excellent yields (79-95%) in liquid ammonia and in DMSO. The N-(ortho-halobenzyl)arylamines are obtained in good to very good isolated yields (44-85%) by nucleophilic substitution of ortho-halobenzylchlorides with different arylamines. The reaction of the anions of a diverse set of N-(ortho-halobenzyl)arylamines was studied, and the methodology was extended to the synthesis of trispheridine, a natural product, in very good yield. In order to explain the regiochemical outcome of these reactions, a theoretical analysis was performed with DFT methods and the B3LYP functional.

Reactivity of the [ReNR]3+ and [ReN]2+ cores toward bis(diphenylphosphino)amine and its derivatives. Synthesis and crystal structures

The complexes fac-[Re(NMe)Cl3{NH(PPh2)2-P,P′}]1, [ReNCl{NH(PPh2)2-P,P′}2]X (X = Cl 2 or BPh42a), [Re(NMe) Cl2{N(XPPh2)2-X,X′}(PPh3)](X = 0 3, S 4 or Se 8), [Re(NMe)Cl{N(XPPh2)2-X,X′}2](X = S 5 or Se 9), [ReNCl{N(SPPh2)2-S,S′}(PPh3)]6, [ReN{N(XPPh2)2-X,X′)2](X = S 7 or Se 10) and trans-[ReOCl2{N(OPPh2)2-O,O′}(AsPh3)]11 were obtained by treatment of [Re(NMe)Cl3(PPh3)2], [ReNCl2(PPh3)2] or [ReOCl3(AsPh3)2] with the appropriate ligand under different experimental conditions. The structures of complexes 1, 2a and 6 were determined by X-ray crystallography. In 1 and 2a the Re atom is six-co-ordinate in a distorted octahedral configuration, whereas in 6 the Re atom is five-co-ordinate square pyramidal with the N atom in the apical position.

Technetium(V)–nitrido complexes of dithiocarbazic acid derivatives. Reactivity of [TcN]2+ core towards Schiff bases derived from S-methyl dithiocarbazate. Crystal structures of [S-methyl 3-(2-hydroxyphenylmethylene)dithiocarbazato]nitrido(triphenylphosphine)technetium(V) and bis(S-methyl 3-isopropylidenedithiocarbazato)nitridotechnetium(V)

New technetium(V)–nitrido complexes with bi- and tri-dentate Schiff bases, derived from the condensation of various aldehydes and acetone with the methyl ester of dithiocarbazic acid, NH2NHC(S)SCH3, were prepared by substitution or substitution–reduction reactions on the square-pyramidal complexes [TcVNCl2(PPh3)2] and [TcVINCl4]–. The final complexes all maintain the square-pyramidal geometry of the starting compounds with the TcN group in an apical position. The bidentate ligands give rise to mono- and di-substituted complexes, in which they are co-ordinated to the metal through the β-nitrogen atom and the thiol sulphur atom; in monosubstituted complexes, the remaining two positions in the plane of the square pyramid are occupied by triphenylphosphine (PPh3) and Cl– groups. The tridentate Schiff bases co-ordinate to the metal, in the basal plane, as doubly negatively charged ligands through the phenolic oxygen atom, the β-nitrogen atom, and the thiol sulphur atom, the fourth position being occupied by the phosphorus atom of a PPh3 group. The crystal structures of [TcNL1(PPh3)](1)[H2L1=S-methyl 3-(2-hydroxyphenylmethylene)dithiocarbazate] and [TcN(L12)2](2)(HL12=S-methyl 3-isopropylidenedithiocarbazate) have been determined. Relevant crystal data for (1) are: refined from 5 008 reflections with I 3σ(I) to a final R of 0.029, crystals are triclinic, space group P, with unit-cell dimensions a= 8.309(1), b= 12.294(1), c= 13.308(3)A, α= 96.22(1), β= 95.07(1), γ= 101.34(1), and Z= 2; for (2): refined from 1 756 reflections with I 3σ(I) to a final R of 0.023, crystals are monoclinic, space group I2/a, with unit-cell dimensions a= 16.707(3), b= 8.838(1), c= 12.514(2)A, β= 106.85(1)°, and Z= 4. In both complexes, the co-ordination around Tc is distorted square pyramidal with an apical multiply bonded nitrogen atom [TcN 1.611(3)A in (1) and 1.613(3)A in (2)] and the basal ligands bent away from the nitrido group.

Room-temperature and transition-metal-free Mizoroki-Heck-type reaction. Synthesis of E-stilbenes by photoinduced C-H functionalization.

We report a conceptually different approach toward E-stilbene syntheses by photoinduced direct C-H arylation of alkenes at rt without the addition of transition metals, with a broad range of aryl halides, including ArI, ArBr, and even ArCl. This is the first time that this reaction has been produced without extra solvent but with 18-crown-6 ether and t-BuOK in only 15 min of reaction.

Reactivity of rhenium(V) complexes containing different cores such as [ReO]3+, [ReNR]3+ and [ReN]2+ toward bis(diphenylphosphino)methane: synthesis and crystal structures

The complexes fac-[ReOCl3(dppm-P,P′)] (1a), mer-[ReOCl3(dppm-P,P′)] (1b), mer-[ReCl3(dppm-P,P′)(dppom-P)] (2), [ReCl4(dppom-P,O)] (3) and mer-[ReCl3(dppm-P,P′)PPh3] (4) (dppmPh2PCH2PPh2, dppomPh2PCH2P(O)Ph2) were obtained by reaction of [ReOCl3(PPh3)2] or [AsPh4][ReOCl4] and dppm under different experimental conditions. Complex 1b is probably obtained via the intermediate formation of complexes 2 or 4. The complexes fac-[Re(NCH3)Cl3(dppm-P,P′] (5), trans-[ReNCl2(dppm-P)PPh3] (6) and [ReNCl(dppm-P,P′)2]Cl (7) were also obtained starting from [Re(NCH3)Cl3(PPh3)2] and [ReNCl2(PPh3)2], respectively. The structures of 1a and 3 were determined by X-ray crystallography. Compound 1a is monoclinic, space group P21/c, with a=11.156(4), b=17.264(5), c=14.467(5) A and β=110.96(3)°. The molecular complex is distorted octahedral. Selected bond distances (A) are: ReO(oxide) 1.671(6), ReCl(trans to O) 2.452(3), ReCl(trans to P) 2.365(4) and 2.373(3), ReP 2.439(3) and 2.449(2). The PReP chelation angle is 69.2(1)°. Compound 3 is orthorhombic, space group Pccn, with a=34.843(5), b=8.242(2) and c=19.342(4) A. The molecular complex is roughly octahedral with the oxidized dppm ligand chelated through the P atom and the O atom of the PO group. Selected bond distances (A) are: ReCl(trans one other) 2.355 (mean), ReCl(trans to P) 2.353(3), ReCl(trans to O) 2.215(5), ReO 2.087(7). The PReO chelation angle is 80.7(2)°.

Photostimulated reactions of haloarenes with 2-naphtylamide ions. A facile synthesis of 1-aryl-2-naphthylamines.

Abstract The photostimulated reactions of aryl iodides with 2-naphthylamide ions in liquid ammonia gave 1-aryl-2-naphthylamines as the major substitution product. This reaction is proposed to occur by the S RN 1 mechanism of nucleophilic substitution

Synthesis of 6-Substituted 2-Pyrrolyl and Indolyl Benzoxazoles by Intramolecular O-Arylation in Photostimulated Reactions

The synthesis of a series of 6-substituted 2-pyrrolyl and 2-indolyl benzoxazoles by photostimulated C-O cyclization of anions from 2-pyrrole carboxamides, 2-indole carboxamides, or 3-indole carboxamides has been found to proceed in good to excellent yields (41-100%) in DMSO and liquid ammonia. The pyrrole and indole carboxamides are obtained in good to very good isolated yields by an amidation reaction of different 2-haloanilines with 2-carboxylic acid of pyrrole and 2- or 3-carboxylic acid of indole. To explain the regiochemical outcome of these reactions (C-O arylation vs C-N or C-C arylation), a theoretical analysis was performed using DFT methods and the B3LYP functional.

Synthesis of Benzo-fused Heterocycles by Intramolecular α-Arylation of Ketone Enolate Anions

A two-step synthesis of six-, seven-, eight-, and nine-member benzo-fused heterocycles in good to excellent yields is reported. The synthetic strategy involves the generation of a new intramolecular α-aryl ketone bond by the photostimulated S(RN)1 reaction of ketone enolate anions linked to a pendant haloarene as the key step. On the other hand, an intramolecular C(Ar)-C(Ar) coupling led to the formation of five- and six-member benzo-fused heterocycles (9H-carbazole and phenanthridine) when an aromatic amide anion is competitively formed.

REACTIONS OF N-THIOACETYLMORPHOLINE ANION WITH IODOARENES AND 1-IODOADAMANTANE BY THE SRN1 MECHANISM

Abstract The anion of N-acetylthiomorpholine 2 was studied in photostimulated reactions with iodobenzene 1a and 1-iodonaphthalene 1b in DMSO, giving good yields of the substitution products 3a and 3b by the S RN 1 mechanism. The reaction of 1a with 2 is also induced with FeBr 2 . 1-Iodoadamantane 4 did not react with the anion of N-acetylmorpholine, but reacted with 2 to give the substitution product 5 under irradiation. By competition experiments, acetophenone enolate ions are 1.4 times more reactive than 2 toward 1a and 3.3 times toward 4 .