Chiral Metal Template Promoted Asymmetric Pyrrole Diels−Alder Reaction between N-(Diphenylphosphino)pyrrole and Diphenylvinylphosphine

Abstract

An organoplatinum complex containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used to promote the asymmetric [4 + 2] Diels-Alder reaction between diphenylvinylphosphine and N-(diphenylphosphino)pyrrole. The reaction was complete in 7 days at room temperature, with the formation of three isomeric chelating diphosphine exo cycloadducts in the ratio 10:3:1. The cycloadducts are thermodynamically unstable and undergo retro-cycloaddition reactions slowly in solution. When the major isomer of the pyrrole cycloadducts was heated with 2-(diphenylphosphino)furan, the respective furan cycloadducts were formed via the retro pyrrole Diels-Alder pathway, followed by an asymmetric furan Diels-Alder reaction. The cyclic diene N-(diphenylphosphino)pyrrole was regenerated from this retro cycloaddition reaction. The undesired retro Diels-Alder reaction could be deterred by hydrogenation of the azanorbornene double bond. The chiral naphthylamine auxiliary could be removed chemoselectively from the metal template by treatment with concentrated hydrochloric acid to generate the corresponding dichloroplatinum(II) complex. The azabicyclic skeleton and the P-N bond remained unchanged in this acid treatment. Further treatment of the dichloro complex with aqueous cyanide liberates the chiral diphosphine cycloadduct, which could be coordinated to the Au-(I) metal ion.

Gold–Gold Interactions

“…Shorter intramolecular aurophilic interactions have been found in the quaterthiophene than in the bithiophene derivative. Chains are obtained for Z ¼ C:C (whose luminescent properties have been studied), trans-CH¼CH, and CH 2 C(¼CH 2 )CH 2 [197][198][199][200][201][202][203][204][205][206][207][208].…”

Chiral Platinum(II) Compounds Containing Ferrocenyl Schiff Bases Acting as (N), (N,O)–, [C(sp2,ferrocene),N]– or [C(sp2,ferrocene),N,O]2– Ligands

“…[1][2][3][4][5][6][7][8][9][10][11] It is well known that compounds of this kind are useful in homogeneous catalysis [3][4] and as chiral derivatising agents, [5] as reagents to determine enantio-or diastereomeric excesses of organic substrates, [6] or even due to their antitumoral activity. [1c,7] Of the examples reported, those having a bidentate [C(sp 2 ,aryl),N] -group are particularly relevant.…”

“…[1c,7] Of the examples reported, those having a bidentate [C(sp 2 ,aryl),N] -group are particularly relevant. [1,3,6,[8][9][10][11] The utility of chiral pallada-and platinacycles in asymmetric catalytic processes [8] including asymmetric Claisen rearrange- [ 2-(in 10 and 11) group. The X-ray crystal structures of 1b·H 2 O, 3b, 7b·CH 2 Cl 2 ·1/2H 2 O and 9a are also reported.…”

“…Notably, Leung et al [11] have recently described the first example of a platinacycle that promotes the asymmetric [4+2] Diels-Alder reaction between diphenylvinylphosphane and N-(diphenylphosphanyl)pyrrole.…”

Three types of reactions with intramolecular five-membered ring compounds in organic synthesis

“…By using bulky chiral cyclo-metalated compounds, some asymmetric Diels-Alder reactions proceed at the metal [84][85][86][87][88]. For example, the organopalladium complex containing the (S)-form of ortho-palladated (1-(dimethylamino)ethyl)-naphthalene has been used successfully as a chiral template to promote asymmetric cyclo-addition reactions between coordinated 3,4-dimethyl-1-phenylphosphole 27-1 and a dienophile (N,N-dimethy lacrylamide or styrene) via an endo pathway, that proceed to give the compound 27-2 as shown in Eq.…”