Enantioselective synthesis of axially chiral l-(naphthyl) isoquinolines and 2-(1-naphthyl)pyridines through sulfoxide ligand coupling reactions.

W. Baker, Robert and O. Rea, Simon and V. Sargent, Melvyn and M.C.S., Elisabeth and Tjahjandarie, Tjitjik Srie and Totaro, Angela (2005) Enantioselective synthesis of axially chiral l-(naphthyl) isoquinolines and 2-(1-naphthyl)pyridines through sulfoxide ligand coupling reactions. Tetahedron, 61 (15). pp. 3613-3880. ISSN 0040-4020

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Abstract

Racemic 1-(1′-isoquinolinyl)-2-naphthalenemethanol rac-12 was prepared through a ligand coupling reaction of racemic 1-(tert-butylsulfinyl)isoquinoline rac-7 with the 1-naphthyl Grignard reagent 10. Resolution of rac-12 was achieved through chromatographic separation of the Noe-lactol derivatives 14 and 15, providing (R)-(−)-12 of >99% ee and (S)-(+)-12 of 90% ee. The ligand coupling reaction of optically enriched sulfoxide (S)-(−)-7 (62% ee) with Grignard reagent 10 furnished rac-12, with the absence of stereoinduction resulting from competing rapid racemisation of the sulfoxide 7. Reaction of optically enriched (S)-(−)-7 with 2-methoxy-1-naphthylmagnesium bromide was also accompanied by racemisation of the sulfoxide 7, and furnished optically active (+)-1-(2′-methoxy-1′-naphthyl)isoquinoline (+)-3b in low enantiomeric purity (14% ee). The absolute configuration of (+)-3b was assigned as R using circular dichroism spectroscopy, correcting an earlier assignment based on the Bijvoet method, but in the absence of heavy atoms. Optically active 2-pyridyl sulfoxides were found not to undergo racemisation analogous to the 1-isoquinolinyl sulfoxide 7, with the ligand coupling reactions of (R)-(+)- and (S)-(−)-2-[(4′-methylphenyl)sulfinyl]-3-methylpyridines, (R)-(+)-17 and (S)-(−)-17, with 2-methoxy-1-naphthylmagnesium bromide providing (−)- and (+)-2-(2′-methoxy-1′-naphthyl)-3-methylpyridines, (−)-18 and (+)-18, in 53 and 60% ee, respectively. The free energy barriers to internal rotation in 3b and 18 have been determined, and the isoquinoline (R)-(−)-12 examined as a ligand in the enantioselectively catalysed addition of diethylzinc to benzaldehyde; (R)-(−)-12 was also converted to (R)-(−)-N,N-dimethyl-1-(1′-isoquinolinyl)-2-naphthalenemethanamine (R)-(−)-19, and this examined as a ligand in the enantioselective Pd-catalysed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate.

Item Type: Article
Uncontrolled Keywords: Axial chirality; Isoquinoline; Pyridine; Sulfoxide; Ligands;Catalysis.
Subjects: Q Science > QD Chemistry
Divisions: 08. Fakultas Sains dan Teknologi > Kimia
Creators:
CreatorsEmail
W. Baker, RobertUNSPECIFIED
O. Rea, SimonUNSPECIFIED
V. Sargent, MelvynUNSPECIFIED
M.C.S., ElisabethUNSPECIFIED
Tjahjandarie, Tjitjik SrieUNSPECIFIED
Totaro, AngelaUNSPECIFIED
Depositing User: Mr Akhmad Nurfizal Reza
Date Deposited: 11 Oct 2017 19:39
Last Modified: 11 Oct 2017 19:39
URI: http://repository.unair.ac.id/id/eprint/61743
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