Towards Asymmetric Catalysis in the Major Groove of 1,1′-Binaphthalenes

Abstract

Four new diphosphane ligands, (R)-4, (R)-5, (S)-6, and (R)-7 (Schemes 3, 4, 6, and 7), featuring metalcoordination sites located in the major groove of chiral 1,1'-binaphthalene clefts, were prepared in enantiomerically pure form. The performance of this new class of ligands was tested in enantioselective, Pdcatalyzed allylic alkylation reactions with acyclic and cyclic methyl carbonates 28 ± 30 as substrates under various reaction conditions (Schemes 8 and 9). Using sodium phenyl sulfinate as a nucleophile, the reactivity of the catalysts formed with the new ligands and suitable palladium precursors was found satisfactory (> 90%); however, the ee values were in all cases poor (< 4%). Slightly better results were obtained using anions of dimethyl malonate as nucleophiles, but, also in these cases, the ee values never exceeded 17% (Table). 31 P-NMRSpectroscopic investigations revealed the formation of multiple-catalyst species in solution (Fig. 2), and molecular modeling suggested a lack of embedding of the coordinated substrate in a chiral pocket (Fig. 3), which probably accounts for the observed low level of enantioselectvity.

Novel [6]‐ and [7]Helicene‐Like Quinones via Mono‐ and Bidirectional Chromium‐Templated Benzannulation of Bridged Binaphthyl Carbene Complexes

“…Besides the diastereomeric camphanate pair 14 and the enantiopure monoquinone 9 derived therefrom, non‐racemic 3 could be obtained from the brominated ( R )‐ or ( S )‐BINOL 1 , which was resolved according to the method published by Diederich 21a…”

Size Matters: Influence of Gold‐to‐Ligand Ratio and Sulfur‐Sulfur Distance of Linear Thioether Heptamers on the Size of Gold Nanoparticles

“…The synthesis of heptamer Ter ( Scheme ) was performed via a one‐pot end‐capping oligomerization strategy with the advantage of making the entire family of oligomers in a single reaction and with the disadvantage that the individual members must be separated by chromatography. For this, precursors 1 and 2 were synthesized as follows: in the first step, mono‐iodination of 1,3,5‐tribromobenzene was achieved following the protocol of Lustenberger and Diederich followed by a standard Suzuki–Miyaura protocol with 1,3‐di‐ tert ‐butylphenylboronic acid in toluene and H 2 O giving compound 4 in yield of 60% over two steps. Subsequent Suzuki coupling with 4 and p ‐tolylboronic acid in tetrahydrofuran (THF) and H 2 O gave compound 3 in 90% yield.…”

“…Considering the synthesis towards AuNPs coated by heptamer Xyl, the more gold salt used for the reaction (8,16,32, and 64 equiv. ), the more reddish the solution appeared, while in the case of 16 equiv.…”

Synthesis of a Hexagonal Nanosized Macrocyclic Fluorophore with Integrated Endotopic Terpyridine Metal‐Chelation Sites

“…Pure 8 was therefore obtained by way of 7 . The reaction between 7 16 and TMSA in Et 3 N with CuI and [PdCl 2 (PPh 3 ) 2 ] catalysts proceeded very selectively at ambient temperature to afford 8 17a, 17b in 93 % yield after work‐up. Treatment of 8 with one equivalent of n BuLi in Et 2 O at low temperature, followed by quenching the phenyllithium intermediate with 1,2‐diiodoethane provided 9 in 95 % yield after chromatographic purification.…”