Synthesis and catalytic properties of transition metal complexes with [beta]-cyclodextrin-functionalized phosphine ligands

Abstract

Reaction of o-Ph2PC6H4CHO with 6-H2NCH2CH2CH2NH-β-CD produced the potentially tridentate mixed donor iminophosphine β-cyclodextrin (6-(o-Ph2PC6H4CH=NCH2CH2NH)-β-CD) (CDNNP). Reactions of CDNNP with MCI2(COD) (M = Pt, Pd) (COD = 1,5-cyclooctadiene) and [Pd(η3-C3H5)Cl]2 produced their platinum and palladium complexes. Reaction of mono-6-trifluoromethanesulfonyl permethylated β-cyclodextrin with (2S,4S)-(-)-(diphenylphosphino)-2-(diphenylphosphinomethyl) pyrrolidine in the presence of proton sponge in CH2Cl2 produced the mono-6-N-[4'-(diphenylphosphino)-2'-(diphenylphosphinomethyl)-pyrrolidinyl)]-6-deoxy permethylated β-cyclodextrin (PMβ-CDPPM). Mono-6-N-[4'-(diphenylphosphino)-2'-(diphenylphosphinomethyl)-pyrrolidinylmethyl-o-benzyl]-6-deoxy permethylated β-cyclodextrin (PMβ-CD-o-Ph-PPM) and mono-6-N-[4'-(diphenylphosphino)-2'-(diphenylphosphinomethyl)-pyrrolidinylmethyl-m-benzyl]-6-deoxy permethylated β-cyclodextrin (PMβ-CD-m-Ph-PPM) were also synthesized. Reactions of PtCl2(COD) and [Rh(COD)2]BF4 (COD = 1,5-cyclooctadiene) with PMβ-CDPPM, PMβ-CD-o-Ph-PPM and PMβ-CD-m-Ph-PPM produced their platinum and rhodium complexes. 6A,6X-bis(trifluoromethanesulfonyl) permethylated β-cyclodextrins (X = B, C and D) were synthesized by the reactions of 6A,6X-dihydroxy permethylated β-cyclodextrins (X = B, C and D) with trifluoromethanesulfonic anhydride in the presence of 2,4,6-tri(tert-butyl)pyridine. Reaction of mono-6-trifluoromethanesulfonyl permethylated β-cyclodextrin with LiPPh2 produced monophosphine PMβ-CDP. Reactions of 6A,6X-bis(trifluoromethanesulfonyl) permethylated β-cyclodextrins (X= B, C and D) with LiPPh2 produced diphosphines 6A,6X-PMβ-CDP2 (X= B, C and D). Reactions of 6A,6X-PMβ-CDP2 (X= B, C and D) with [Rh(COD)2]BF4 and PtCl2(COD) (COD = 1,5-cyclooctadiene) produced their rhodium and platinum complexes. (S,S)-4,5-Bis(diphenylphosphino)-2-(3’-hydroxypheny1)-1,3-dioxolane (m-OH-Bz-DIOP) was synthesized by the reaction of m-hydroxybenzaldehyde with (2S,3S)-dihydroxy-1,4-bis(diphenylphosphino)butane in the presence of p-toluenesulfonic acid in dry benzene. Reaction of (S,S)-4,5-Bis(diphenylphosphino)-2-(3'-hydroxyphenyl)-1,3-dioxolane with mono-6-trifluoromethanesulfonyl permethylated β-cyclodextrin in the presence of NaH in THF gave β-cyclodextrin-functionalized DIOP ligand (PMβ-CD-m-DIOP). The analogous ligand PMβ-CD-p-DIOP could be prepared by similar procedure starting from p-hydroxybenzaldehyde. Their rhodium and platinum complexes have been synthesized. The β-cyclodextrin-functionalized phosphines have been evaluated for rhodium-catalyzed asymmetric hydrogenation, palladium-catalyzed allylic alkylation and palladium-catalyzed allylic amination