Dye-sensitized photooxygenation

Some unusual pyridazine syntheses were reported. A dye-sensitized photooxygenation reaction of ribofuranosyl furans gave a new entry to pyridazine C-nucleosides 14... 

Wittig reaction of 10 with pentyl phosphonium salt in the presence of NaH gave Z-olefin 11 selectively. Dye-sensitized photooxygenation of 11 proceeded exclusively to give the endoperoxides 12a and 12b in almost quantitative yield as a roughly 1 1 mixture of two diastereomers. 

The oxaziridine ring system has been formed by the oxidation of C=N double bond . The two-step synthesis of iV-phosphinoyloxaziridines 16 from oximes 15 was described (equation 7) . Irradiation of hydroperoxynitrones 18, prepared by dye-sensitized photooxygenation of 2-methoxyfuran in the presence of oximes 17, led to fraw -oxaziridines 19 in yields up to 89% (equation 8) ". ... 

Dye-sensitized photooxygenation of oxazoles (242) in aprotic solvents with 650 W halogen lamp leads to unstable 1,2,4-dioxazolines (244) via intermediate cyclic peroxides (243) (Scheme 49) <90JCS(Pl)10n, 91JCS(P2)1085>. 

Arteflene (5) >7 steps (A) Dye-sensitized photooxygenation (Ene reaction) 35 nM (Kl) 20 mgkg Metabolism and toxicity studies completed prior to phase 2 clinical trials 14... 

Similarly, indenes undergo dye-sensitized photooxygenation at — 78°C in acetone to yield the usual oxygenated products, namely 2,3 7,9-diepoxy-6,9-peroxy-A4,5-hexahydroindenes (93). These compounds also undergo thermal rearrangement to form indene tetraepoxides (benzene oxides) (94) and are converted to 2,3 4,9 7,8-triepoxy-A5-6-hexahydroindenes (95) on treatment with trimethyl phosphite.49... 

In connection with the above discussion, formation of 3,3-disubsti-tuted 2 (3 H)-oxepinones (73) in the dye-sensitized photooxygenation of 6,6-disubstituted fulvenes is of special interest. 57>58> The reaction may be pictured in terms of an allene oxide intermediate which, as shown in Scheme 11, isomerizes to a cyclopropanone, followed by intramolecular rearrangement. 

Astarita, A., Cermola, F., Iesce, M.R., and Previtera, L. (2008) Dye-sensitized photooxygenation of sugar fiirans novel bis-epoxide and spirocydic C-nudeo-sides. Tetrahedron, 64 (28), 6744—6748. 

In this chapter we review the synthesis of organic peroxides from singlet molecular oxygen [102 )] via dye-sensitized photooxygenations. The chapter comprises four... 

The dye-sensitized photooxygenation of oxazoles with alkoxy substituents in positions 2, 4 or 5 gives 1,2,4-dioxazoles, e.g. (176). These novel heterocycles are believed to arise by addition of oxygen to the 4,5-double bond leading to peroxiranes, such as (175), as the primary intermediates (equation 20). 

In the dye-sensitized photooxygenation of enamines, the carbon-carbon double bond is cleaved by singlet oxygen to give a ketone (or aldehyde) and an amide4,5 (Scheme 1). 

Other examples of reactions closely related to the Diels-Alder cycloaddition reaction are the ene reactions between alkenes with allylic hydrogen atoms (ene) and compounds with a double bond (enophile) [135, 136], and the dye-sensitized photooxygenation of allylic alkenes by singlet oxygen to give allylic hydroperoxides with a shifted double bond [137-139]. 

A study of the dye-sensitized photooxygenation of the carbon-nitrogen double bond has revealed a reactivity pattern of C-N compounds towards 02 which suggests that reaction is facilitated by electron donors attached to... 

Dye-sensitized photooxygenation of l-alkyl-2(l//)-pyrazinones (97) gives endoperoxides (98), the... 

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