Cycloadditions in syntheses. XXXII Intramolecular photocycloaddition of 4-(.OMEGA.-alkenyloxy)quinolin-2(1H)-one : Synthesis of 2-substituted cyclobuta[c]quinolin-3(4H)-ones.

Enantioselective Intramolecular [2+2]-Photocycloaddition Reactions in Solution

“…[18] The application of the enantioselective photocycloaddition is not restricted to the formation of the crossed photocycloaddition product 2. A high enantiomeric excess was also recorded in the photocycloaddition of substrate 6 [12] which was converted enantioselectively into cyclobutane (À)-7 (Scheme 3). The product (88 % ee) was isolated in 88 % yield.…”

“…For our studies we have selected the 2-quinolone 1, which upon irradiation with UV light cleanly yields the chiral cyclobutane (À)-2 and its enantiomer ()-2 by an intramolecular [22]-photocycloaddition. [12] The simple diastereoselectivity of the reaction is high; only a single diastereoisomer is formed, as shown in Scheme 1. As host compounds, the bicyclic lactams (À)-4 and ()-5 were prepared (Scheme 2).…”

Enantioselektive Katalyse photochemischer Reaktionen

“…Das Produkt 29 wurde unter optimierten Bedingungen bei Verwendung von 100 Mol-% Katalysator in 22 % ee, von 50 Mol-% in 20 % ee und von 25 Mol-% in 19 % ee erhalten, wobei die Reaktionsdauer bis zum vollständigen Umsatz von der Katalysatormenge abhing. [43] Überraschen-derweise wurde das in den Arbeiten von Kaneko et al [44] zu dieser Reaktion gefundene Nebenprodukt 30 nicht beobachtet.…”

Light‐Driven Enantioselective Organocatalysis

“…[8] This particular transformation was selected as test reaction, because it delivers a cycloaddition product by a rapid five-membered ring closure, [9] and because it had already been shown by Krische et al [10] that a sensitization of this reaction is possible by a chiral benzophenone (19 % ee with 25 mol % catalyst). The latter result provided hope that a catalytic reaction course might be feasible with the benzophenone 4 described earlier.…”