1,2-Bis(anilido)ethane Complexes of Calcium and Potassium: Synthesis, Structures, and Catalytic Activity

Abstract

The metalation of 1,2-bis­(anilino)­ethane with excess KH leads to the formation of the potassium complex [(thf)3K2{1,2-(PhN)2C2H4}] (1). Complex 1 quantitatively reacts with anhydrous CaI2 in THF yielding insoluble KI and dinuclear [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) after crystallization from a mixture of THF and hexane. Addition of N,N,N′,­N′′,N′′′,N′′′-hexa­methyl­triethylene­tetraamine (hmteta) yields [(hmteta)­Ca­{1,2-(PhN)2C2H4}] (3). The complexes 1 and 2 proved to be inactive as catalysts in hydroamination reactions of diphenylbutadiyne with secondary amines. However, a mixture of 1 and 2 (K:Ca ratio of 2:1) mediated the addition of N-methyl-aniline and 1,2-bis­(anilino)­ethane to one of the CC triple bonds of diphenylbutadiyne. Addition of 18-crown-6 ether (18C6) leads to the formation of the sparingly soluble potassium complex [{(18C6)­K}2{1,2-(PhN)2C2H4}] (5) and the insoluble calcium complex [(18C6)­Ca­{1,2-(PhN)2C2H4}] (6). The calciate-mediated hydroamination reaction is regiocontrolled, but E- and Z-isomeric addition products are observed, regardless of whether the reaction is performed at daylight or in the dark. If toluene is used as solvent for this s-block metal-mediated hydroamination catalysis, (Z,Z)-1,4,5,8,9,12-hexaphenyl-5,8-diazadodeca-3,9-diene-1,11-diyne (Z,Z-8) precipitates, allowing isolation and characterization of this isomer. In solution, this compound isomerizes upon irradiation yielding an equilibrium between (Z,Z)-, (E,Z)- and (E,E)-isomers. The determination of the crystal structures of (Z,Z)- and (E,E)-1,4,5,8,9,12-hexaphenyl-5,8-diazadodeca-3,9-diene-1,11-diyne unequivocally allows the assignment of the NMR parameters to specific isomers.

Catalytic Hydrofunctionalization Reactions of 1,3-Diynes

“…In an additional work, Westerhausen and colleagues attempted the generation of cyclic butadiene derivatives by double hydroamination of PhC≡CC≡CPh with a linear diamine, i.e., N,N -diphenylethylenediamine. The expected cyclic product was not formed, the reaction yielding compound 73, resulting from the addition of the diamine to two molecules of the diyne (Figure 11) [117]. For this particular transformation, the resulting complex Intramolecular hydroamination reactions of 1,3-diynes functionalized with pendant amino groups have also been described.…”

Nascent developments in main group element-catalyzed hydrosilylation and dehydrogenative silylation of alkenes and alkynes

“…47 All these factors make them attractive and sustainable catalysts for several organic transformations even though their redox chemistry and the number of oxidation states are restricted. 47 Recently, alkali metal-based catalysts were employed in hydroboration, 48,49 intra-and intermolecular hydroamination, 50,51 hydrogenation, 52,53 transfer hydrogenation, 54 dehydrogenation, 55 and Brønsted base catalyzed C-C addition reactions. [56][57][58] Of course, these catalysts are also utilized in the hydrosilylation of carbonyl compounds.…”

Hydroelementation of diynes

“…The authors discussed in detail the mechanisms of these transformations, which differ according to the hydroamination reagent. 294…”

“…[19][20][21][22]29,[289][290][291][292][293] This 100% atom economic method mostly requires the application of a catalyst to (i) overcome the repulsion electrostatic effect between the high electron-dense unsaturated CRC bond and the strong Lewis base (electron-rich amine 11 or 21, ammonia, or hydrazine), and (ii) to facilitate this addition reaction due to the high energy difference between both types of bonds. 294 The hydroamination of (non)conjugated diynes leads to various products, but intramolecular cyclisation is of utmost importance to produce N-heterocyclic compounds, e.g., indoles, pyrroles, pyrazoles, pyrimidines.…”