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1‐Methoxycarbonyl‐substituiertes 2,3‐Dihydropyridin‐4(1 H )‐on (= Methyl‐1,2,3,4‐tetrahydro‐4‐oxopyridin‐1‐carboxylat) als Chromophor für die photochemische [2 + 2]‐Cycloaddition
Author(s) -
Guerry Philippe,
Blanco Philippe,
Brodbeck Heinz,
Pasteris Olivier,
Neier Reinhard
Publication year - 1991
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19910740118
Subject(s) - chemistry , cycloaddition , substituent , olefin fiber , regioselectivity , ring (chemistry) , medicinal chemistry , chromophore , selectivity , stereochemistry , photochemistry , catalysis , organic chemistry
1‐Methoxycarbonyl‐Substituted 2,3‐Dihydropyridin‐4(1 H )‐one(= Methyl 1,2,3,4‐Tetrahydro‐4‐oxopyridine‐1‐carboxylate) as Chromophore for Photochemical [2 + 2]‐Cycloadditions With olefins having an electron‐acceptor as well as with olefins having an electron‐donor substituent, 1‐methoxycarbonyl‐substituted dihydropyridinone 12 undergoes [2 + 2] cycloaddition in good preparative yields. The photochemical cycloaddition is highly regioselective. For preparative purposes, the ring junction can be equilibrated to the thermodynamically more stable cis ‐junction. Only the ‘ endo ’/‘ exo ’ selectivity at the C‐atom bearing the olefin substituent cannot be controlled. The photodimerization of 12 is the only side reaction. Using a slight excess of the olefin, the photodimerization can be suppressed. The protecting group at the N‐atom of the dihydropyridinone can be varied in order to introduce an internal sensitizer, as shown with 1‐acyl‐substituted compound 29 , which underwent the cycloaddition process even with sunlight.