Unexpected racemization behavior of 8,8′-dialkyl-1,1′-biisoquinoline

Tsue, Hirohito; Fujinami, Hideyuki; Itakura, Takeshi; Hirao, Kazuyuki

doi:10.1016/s0957-4166(99)00305-5

Cited by 4 publications

(2 citation statements)

References 19 publications

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“…The 8,8‘-dialkyl-1,1‘-biisoquinolines (R = Me, Et, i -Pr, t -Bu) have been prepared and are known to racemize slowly at room temperature. − These ligands would be likely to have large dihedral angles, and chelation to metals may not be possible.…”

Section: 2 Atropisomeric Biisoquinolines and Bipyridinesmentioning

confidence: 99%

Use of Achiral and Meso Ligands To Convey Asymmetry in Enantioselective Catalysis

2003

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1. Introduction and Scope 3297 2. The Use of Achiral Salen Ligands in Asymmetric Catalysis 3305 3. Use of Achiral Biphenol-Based Ligands in Asymmetric Catalysis 3308 3.1. Asymmetric Carbonyl−Ene Reaction 3308 3.2. Asymmetric Addition of Methyl Groups to Aldehydes 3309 3.3. Asymmetric Baeyer−Villiger Oxidation 3309 4. Atropisomeric Biphenyl-Based Phosphines and Related Ligands in Asymmetric Catalysis 3310 4.1. Asymmetric Hydrogenation Reactions Using BIPHEP-Derived Ligands 3311 4.2. Asymmetric Diels−Alder and Carbonyl−Ene Reactions with BIPHEP-Derived Ligands 3313 4.3. Interconversion of Diastereomeric Catalysts and Catalyst Precursors Containing BIPHEP Derivatives 3315 4.4. Mechanistic Aspects of Atropisomerization of BIPHEP 3317 4.5. A Potentially Useful New Class of Achiral Diphosphine Ligands (NUPHOS) 3319 4.6. Complexes of a Meso Cyclohexane-Based Diphosphine 3320 4.7. Spontaneous Resolution of an Asymmetric Catalyst Bearing a Bis(phosphole) Ligand 3320 4.8. A Metallocene Catalyst with a Biphenyl Backbone 3322 4.9. Use of Bis(diphenylphosphino)ferrocene and Related Ligands in Asymmetric Catalysis 3323 4.10. Dynamic Resolution of Bis(phospholyl)−Zr Complexes 3325 5. Examination of the Barrier to Atropisomerization in Biphenyl-Based Diamines 3326

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Section: 2 Atropisomeric Biisoquinolines and Bipyridinesmentioning

confidence: 99%

Use of Achiral and Meso Ligands To Convey Asymmetry in Enantioselective Catalysis

2003

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“…Fixing of the latter permits complex formation with Ru(II) or Os(II) [16,17]. Introduction of a substituent into position 8 increases the energetic barrier to rotation and hence for 8,8'-dialkyl-1,1'-bisisoquinolines also makes possible the formation of atropoisomers [18][19][20].…”

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confidence: 99%

Symmetrical and Unsymmetrical Bis-1,1′-(3,4-dihydroisoquinolines)

Глушков

Karmanov

Shklyaev

2005

Chem Heterocycl Compd

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Shklyaev3,3,-Dialkyl-1-cyano-3,4-dihydroisoquinolines were prepared by Beckmann defragmentation of ethyl α-(3,3-dialkyl-3,4-dihydroisoquinol-1-yl)-α-hydroximinoacetates and they take part in a Ritter reaction to form substituted bis-1,1'-(3,4-dihydroisoquinolines).As heterocyclic analogs of 1,1'-binaphthyl systems, bis-1,1'-isoquinolines are promising ligands for the preparation of metallocomplex catalysts since coordination with a metal is possible at the nitrogen atoms [1]. A method is known for the Ullman preparation [2] of bis-1,1'-isoquinolines while 3,4-dihydro derivatives are not formed under these conditions and they are rather inaccessible compounds. Bis-1,1'-(3,4-dihydroisoquinolines) unsubstituted in position 3 have been previously obtained using a Bischler-Napieralski reaction by the action of POCl 3 in acetonitrile [3] or Tf 2 O in the presence of 4-N,N-dimethylaminopyridine [4] on the corresponding oxamide. In the current work we propose a route to bis-1,1'-(3,4-dihydroisoquinolines) which is based on the Ritter reaction [5,6].A second order Beckmann rearrangement [7,8] of ethyl α-(3,3-dialkyl-3,4-dihydroisoquinol-1-yl)-αhydroximinoacetates 1a-c using the method [9, 10] gave the nitriles 2a-c. Despite the simplicity it should be noted that the indicated method is poorly reproducible in our hands, the yields of the products 2 differing markedly from one experiment to another.The nitrile 2a was also prepared by the dehydration of 3,3-dimethyl-3,4-dihydroisoquinolylaldoxime 3 [11] in refluxing xylene using a known method [12] (see Experimental section. The hydrochloride 3.HCl has been reported before [13]).The Ritter reaction of nitriles 2a-c and carbinols 4a-c (stirring the reagents in a mixture of toluene and conc. H 2 SO 4 at 20°C) gave 42-71% yields of compounds 5a-e (Tables 1 and 2). According to this scheme another combination of nitrile and carbinol is possible which leads to both symmetrical and unsymmetrical bis-1,1'-(3,4-dihydroisoquinolines) 5. Compound 5c was also prepared in somewhat lower yield (37%) by the condensation of nitrile 2b with veratrole and isobutylene oxide using method [14] (Scheme 1).A feature of the 1 H NMR spectrum of compound 5b is the small shift of the H-8 signal of the 6,7-dimethoxy-substituted ring to high field by about 0.2 ppm when compared with the H-8 signal of 6,7-dimethoxy-1,3,3-trimethyl-3,4-dihydroisoquinoline [14] and this is due to the anistropic effect of the neighboring 3,4-dihydroisoquinoline fragment. A similar high field shift caused by a benzene ring has previously been observed by us in the case of 6,7-dimethoxy-3,3-dimethyl-1-phenyl-3,4-dihydroisoquinoline [14].0009-3122/05/4104-0475©2005 Springer Science+Business Media, Inc. nitrile 2b (0.3 g, 1.23 mmol) and carbinol 4a (0.2 ml, 1.25 mmol) in toluene (20 ml) was added to conc. H 2 SO 4 (10 ml) and the mixture obtained was stirred for 2 h at 20°C and poured into water (100 ml).The aqueous layer was separated, washed with toluene (15 ml) and NH 4 OH (25%) was then added to pH ~ 8. The product was ext...

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