Preparation of chiral phosphorus, sulfur and selenium containing 2-aryloxazolines

Peer, M.; Jong, Johannes C. de; Kiefer, Matthias; Langer, Thomas; Rieck, Heiko; Schell, H.; Sennhenn, Peter; Sprinz, Jürgen; Steinhagen, Henning; Wiese, Burkhard; Helmchen, Günter

doi:10.1016/0040-4020(96)00267-0

Cited by 138 publications

(71 citation statements)

References 31 publications

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“…dt, J = 7.4, 1.1 Hz, 1H), 7.26 (app. dt, J = 7.7, 1.8 Hz, 1H), 6.24 (bd, J = 8.1 Hz, 1H), 4.05 (m, 1H), 3.93 (dd, J = 11.4, 3.6 Hz, 1H), 3.66 (dd, J = 11. 4 …”

Section: (S)-leucinol and (S)-tryptophanol Were Purchased From Sigma-mentioning

confidence: 99%

A Facile and Modular Synthesis of Phosphinooxazoline Ligands

et al. 2007

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Materials and Methods. Unless otherwise stated, reactions were performed in flamedried glassware under an argon or nitrogen atmosphere using dry deoxygenated solvents. Solvents were dried by passage through an activated alumina column under argon. Diphenylphosphine, di-p-tolylphosphine, dicyclohexylphosphine, and diisobutylphosphine were purchased from Strem Chemicals, Inc. and were used as received. Copper (I) iodide, N,N′-dimethylethylenediamine, cesium carbonate, 2-bromobenzoyl chloride, tetrafluoroboric acid solution and molecular sieves 4Å were purchased from Sigma-Aldrich Chemical Company and used as received. Bis-(4-(trifluoromethyl)phenyl)phosphine was prepared by the known method. 1 (S)-Leucinol and (S)-tryptophanol were purchased from Sigma-Aldrich Chemical Company and Chem-Impex International, Inc., respectively. The other starting chiral amino alcohols were prepared by the reduction of the corresponding amino acids, 2 which were purchased from Chem-Impex International, Inc. 2-Bromo-5-methoxybenzoyl chloride and 2-bromo-5-(trifluoromethyl)-benzoyl chloride were prepared from the corresponding benzoic acid derivatives. 3Reaction temperatures were controlled by an IKAmag temperature modulator. Thin-layer chromatography (TLC) was performed using E. Merck silica gel 60 F254 precoated plates (0.25 mm) and visualized by UV fluorescence quenching, anisaldehyde, CAM, or KMnO 4 staining. ICN Silica gel (particle size 0.032-0.063 mm) was used for flash chromatography. Optical rotations were measured with a Jasco P-1010 polarimeter at 589 nm.

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“…dt, J = 7.4, 1.1 Hz, 1H), 7.26 (app. dt, J = 7.7, 1.8 Hz, 1H), 6.24 (bd, J = 8.1 Hz, 1H), 4.05 (m, 1H), 3.93 (dd, J = 11.4, 3.6 Hz, 1H), 3.66 (dd, J = 11. 4 …”

Section: (S)-leucinol and (S)-tryptophanol Were Purchased From Sigma-mentioning

confidence: 99%

A Facile and Modular Synthesis of Phosphinooxazoline Ligands

et al. 2007

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“…Nucleophilic aromatic substitution of the F-atom in (2-fluorophenyl)dihydrooxazole by either LiPPh 2 or KPPh 2 has been reported [16]. Accordingly, rac-7b was first reacted with LiPPh 2 ; but on finding that this afforded only traces of 2a, we turned to the more reactive KPPh 2 .…”

Section: Methodsmentioning

confidence: 95%

Synthesis of New Chiral Bidentate (Phosphinophenyl)benzoxazine P,N-Ligands

Kündig

Meier

1999

HCA

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Two new chiral bidentate (phosphinophenyl)benzoxazine P,N‐ligands 2a and 2b were synthesized from highly enantiomer‐enriched 2‐(1‐aminoalkyl)phenols 4. Ligand rac‐2a was obtained on refluxing the t‐Bu‐substituted (aminomethyl)phenol 4a with 2‐(diphenylphosphino)benzonitrile in chlorobenzene in the presence of anhydrous ZnCl2 followed by decomplexation (Scheme 2). This reaction, when carried out with (+)‐(S)‐4a, was accompanied by racemization at the stereogenic center of the alkyl side chain. The enantiomerically pure ligands (+)‐(R)‐2a and (−)‐(S)‐2a were obtained using a stepwise procedure via the amides (−)‐(R)‐ and (+)‐(S)‐5b, respectively, followed by cyclization to benzoxazines (+)‐(R)‐ and (−)‐(S)‐7b, respectively, with triflic anhydride and by F‐atom substitution by diphenylphosphide (Schemes 3 and 5). In the case of the i‐Pr analogue 2b, this last step resulted in racemization (Scheme 6). This was overcome by preparing the bromo derivative and introducing the diphenylphosphine group via Br/Li exchange and reaction with chlorodiphenylphosphine (Scheme 7). The first application of (+)‐(R)‐2a in an asymmetric Heck reaction showed high enantioselectivity (91%) (Scheme 8).

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“…After treatment of 9 with p-tosyl chloride and triethylamine in CHCl 3 according to ref. [27] the original oxazoline 3a was restored.…”

Section: The 2-(44ј-bipyridin-2-yl)oxazolines 3a-fmentioning

confidence: 91%

“…Hexafluorophosphate (27): From oxazoline 23a. By adding 12 ml of dry ether to the filtrate and cooling to Ϫ20°C a bright orange solid (475 mg, 0.7 mmol, 75%) was obtained.…”

Section: General Procedures III [(η 4 -15-cyclooctadiene)oxazoline-rhmentioning

confidence: 99%