Rhodium catalyzed asymmetric Pauson-Khand reaction using SDP ligands

Abstract

The activity and enantiocontrol ability of the chiral catalysts prepared from spiro diphosphine ligands, SDP, and rhodium precursor were investigated in the asymmetric catalytic Pauson-Khand reaction. The results showed that SDP ligands were very effective in Rh-catalyzed Pauson-Khand reaction, and their complexes with rhodium could convert a variety of 1,6-enyne compounds into bicyclopentone derivatives under CO atmosphere in high yields with good enantioselectivities. The SbF 6 − was found to be a suitable counter anion of the catalyst, and 1,2-dichloroethane was the best choice of the solvent for Pauson-Khand reaction.Transition-metal-catalyzed Pauson-Khand reaction (PKR) [1][2][3][4] can conveniently convert an alkyne, an alkene and a carbon monoxide into cyclopentenone compounds in one step, which widely exist in natural products and bioactive molecules [5,6] . Owing to the wide application in organic synthesis, the Pauson-Khand reaction was extensively studied and a number of catalysts have been developed. Besides cobalt [1][2][3][4] , which was originally used, many other transition metals were applied to catalyze Pauson-Khand reaction [7][8][9][10][11][12][13] . Recently, the asymmetric catalytic version of this reaction has also been realized. The complexes of Ti [14][15][16] , Co [17][18][19] , Ir [20] and Rh [21][22][23] with chiral ligands could serve as catalysts in the enantioselective Pauson-Khand reaction. However, except for the Ti catalyst [(S,S)-(EBTHI)Ti(CO) 2 ], all the catalysts that gave high degree of enantiocontrol contained BINAP and its derivatives as chiral ligands. It is of great interest to find new efficient catalysts that use other types of chiral ligands for asymmetric Pauson-Khand reaction.Recently, a new type of C 2 symmetric diphosphine ligands SDP with a chiral 1,1′ -spirobiindane scaffold have been developed in our laboratory (Scheme 1). The Ru(II) complexes of SDP ligands were proven to be highly efficient for asymmetric hydrogenation of simple ketones (S/C up to 100,000 and ee up to 99.5%) [24] . The Pd(II) complexes of SDP were also excellent catalysts for asymmetric allylic alkylation reactions [25] . During the course of our study on the application of SDP ligands, we became interested in the asymmetric Pauson-Khand reaction. In this paper, we would like to report our results in the investigation on the Rh-catalyzed Pauson-Khand reaction using SDP ligands. Experimental Apparatus and reagentsAll reactions and manipulations were performed 82 Science in China: Series B Chemistry Scheme 1. SDP ligands.under argon or carbon monoxide using standard Schlenk technique. Anhydrous THF, DME, toluene and dioxane were distilled from sodium benzophenone ketyl. DCE and EtOAc were distilled from calcium hydride prior to use. The substrates 1a [7] , 1c [22] , 1d [22] , 1h [16] , 1i [26] , 1j [27] and 1k [26] were prepared by the literature methods. Melting points were measured on an RY-Ι apparatus and uncorrected. 1 H and 13 C NMR spectra were recorded on Brucker 300 MHz. Chemical shifts...

Synthesis of Cyclopentitols by Ring-Closing Approaches

“…The transformation is well-known as both intermolecular and intramolecular versions, the latter being more widely exploited after its introduction in the early 1980s. 187 Several metal carbonyls have been applied as carbon monoxide source instead of dicobalt octacarbonyl, such as molybdenum, [188][189][190][191][192][193][194] titanium, [195][196][197][198][199][200][201][202][203] zirconium, 197,204,205 ferrium, 206 nickel, 207,208 iridium, [209][210][211][212] rhodium, [213][214][215][216][217][218][219][220] and ruthenium 213,[221][222][223][224] carbonyls. More recently, it has been found that PdCl 2 coordinated to a thiourea ligand could also catalyze an intramolecular reaction.…”

“…The transformation is well-known as both intermolecular and intramolecular versions, the latter being more widely exploited after its introduction in the early 1980s . Several metal carbonyls have been applied as carbon monoxide source instead of dicobalt octacarbonyl, such as molybdenum, − titanium, − zirconium, ,, ferrium, nickel, , iridium, − rhodium, − and ruthenium ,− carbonyls. More recently, it has been found that PdCl 2 coordinated to a thiourea ligand could also catalyze an intramolecular reaction. − The classical version of PKR involved a stoichiometric quantity of cobalt carbonyl, while the recent catalytic variants require substoichiometric amounts of cobalt or other transition metals.…”

Development of a One-Step Synthesis of oxa-Spirocyclic Diphosphine Ligands Driven by Their Application in the Industrial Synthesis of Sacubitril

“…Due to their structural rigidity and stability, chiral spiro diphosphine ligands have witnessed great advances . In 2003, Zhou and co-workers reported the design and synthesis of a novel spiro diphosphine ligand, termed as SDP, which has been widely utilized in asymmetric catalysis . In 2012, another novel spiro diphosphine ligand SKP was developed by Ding and co-workers (Figure ).…”

Rhodium-Catalyzed Enantioselective and Desymmetrizative Pauson–Khand Reaction: Access to Tricyclo[6.2.1.04,11]undecenes

“…Alternatively, asymmetric PKRs with other metal catalysts have been explored . Up to date, Rh catalysts have proved to be promising for asymmetric PKRs because of their electrical properties (Scheme B). − Unfortunately, the application of this strategy remains greatly limited by the narrow substrate scope. For example, to the best of our knowledge, only terminal alkenes and allenes were reported in the Rh-catalyzed asymmetric PKRs.…”