Enantioselective Cycloisomerization of 1,5‐Enynes Promoted by Cyclometalated NHC–Pt^II–Monophos Catalysts

Abstract

The enantioselective cycloisomerizations of 1,5-enynes bearing non-migrating oxygen functions at the propargylic carbon atom have been carried out by using Monophos-Pt II and Binepine-Pt II complexes as chiral precatalysts. They afforded the corresponding bicyclo[3.1.0]hexan-3-one in up to 63 % enantiomeric excess. The stereochemical outcome of these

Platinum(II) Catalyzed Enantioselective Cycloisomerizations of 3‐Hydroxylated 1,5‐Enynes

“…In preliminary studies, it was demonstrated that the Monophos complex 1 a (R=Me) gives ee values up to 50–60 % in the cycloisomerization of 1,5‐enynes with OH or O‐TBS functions at the propargylic position. The stereochemical control from the catalyst overcomes the possible effect of the stereogenic center of the substrate 6…”

“…Thus, with the challenging aim of setting enantioselective variants of these reactions, we have investigated the potential of the cyclometalated NHC‐platinum complexes 1 5 as chiral pre‐catalysts for the cycloisomerization of 3‐hydroxylated 1,5‐enynes. The main results of these studies are disclosed hereafter 6…”

Multiformat T‐Cell‐Engaging Bispecific Antibodies Targeting Human Breast Cancers

“…The participation of complexes formed from combinations of chiral bidentate phosphine ligands and achiral monodentate ligands (a phosphine or an N ‐heterocyclic carbene) in the enantioselective Pt‐catalyzed cycloisomerization of 1,5‐dienes,9 1,5‐enynes,10 and 1,6‐enynes11 has also been reported (Scheme , complex B ). A second class of platinum catalysts resulting from the association of an achiral metallacyclic N ‐heterocyclic carbene ligand and a chiral monophosphine ligand has been applied in the cycloisomerization of 1,6‐enynes12 and 1,5‐enynes 13. (Scheme , complex C ).…”

Use of Planar Chiral Ferrocenyl­phosphine‐Gold(I) Complexes in the Asymmetric Cycloisomerization of 3‐Hydroxylated 1,5‐Enynes

“…We prepared enantiomerically pure substrates ( R )‐ 5a and ( S )‐ 5a ,11a and submitted them separately to cycloisomerization, using either enantiopure complex ( S )‐ 4c or the achiral gold complex [(2‐biphenyl)di‐ tert ‐butylphosphine]gold(I)(acetonitrile) hexafluoroantimonate ( 7 ) as the catalyst. When the chiral catalyst [i.e., ( S )‐ 4c ) was used in the cycloisomerization of ( R )‐ 5a and ( S )‐ 5a , enantiomeric excesses of 50 and 38 % ee , respectively, were obtained (Table 4, entries 1 and 2).…”