This Review describes singlet oxygen (1O2) in the organic synthesis of targets on possible 1O2 biosynthetic routes. The visible-light sensitized production of 1O2 is not only useful for synthesis; it is extremely common in nature. This Review is intended to draw a logical link between flow and batch reactions—a combination that leads to the current state of 1O2 in synthesis.

Using Singlet Oxygen to Synthesize Natural Products and Drugs

This review is the first to collate and summarize main data on named and unnamed rearrangement reactions of peroxides. It should be noted, that in the chemistry of peroxides two types of processes are considered under the term rearrangements. These are conventional rearrangements occurring with the retention of the molecular weight and transformations of one of the peroxide moieties after O-O-bond cleavage. Detailed information about the Baeyer-Villiger, Criegee, Hock, Kornblum-DeLaMare, Dakin, Elbs, Schenck, Smith, Wieland, and Story reactions is given. Unnamed rearrangements of organic peroxides and related processes are also analyzed. The rearrangements and related processes of important natural and synthetic peroxides are discussed separately.

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-12-162.pdf

Rearrangements of organic peroxides and related processes

The principle of vinylogy states that the electronic effects of a functional group in a molecule are possibly transmitted to a distal position through interposed conjugated multiple bonds. As an em...

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

2,4,5,6-Tetrakis(3,6-di-tert-butyl-9H-carbazol-9-yl)isophthalonitrile (4CzIPN-tBu) was developed as a photocatalyst for the phosphorus-radical-initiated cascade cyclization reaction of isocyanides. By using 4CzIPN-tBu as catalyst, we developed a visible-light-induced proton-coupled electron transfer strategy for the generation of phosphorus-centered radicals, via which a wide range of phosphorylated phenanthridines, quinolines, and benzothiazoles were successfully constructed.

4CzIPN-tBu-Catalyzed Proton-Coupled Electron Transfer for Photosynthesis of Phosphorylated N-Heteroaromatics.

https://zenodo.org/record/32921/files/SINOXYGEN-2014-004.pdf

Furans and singlet oxygen – why there is more to come from this powerful partnership

A highly adaptable method targeting the ubiquitous and very important pyrrolizidine and indolizidine scaffolds is presented. The general synthetic utility of the method is underscored by its application to the rapid and easy synthesis of five natural products starting from readily accessible alkylfuran precursors. These unprotected primary furylalkylamines are subjected to photooxygenation conditions, which initiate a complex cascade reaction sequence concluding with the production of high value motifs. This sequence can be tailored to need by varying the choice of both photosensitizer and base additive.

Photooxygenation of Furylalkylamines: Easy Access to Pyrrolizidine and Indolizidine Scaffolds.

A highly efficient one-pot transformation of readily accessible furans into 4-hydroxy-2-cyclopentenones in H2O, using singlet oxygen as oxidant, has been developed.

/pdf/one-pot-transformation-of-simple-furans-into-4-hydroxy-2-4dxwx3ugxz.pdf

One‐Pot Transformation of Simple Furans into 4‐Hydroxy‐2‐cyclopentenones in Water

Very recent investigations are described, which have shown how basic and unprotected nitrogen functionalities can be included, problem-free, in the furan photooxidation step of singlet oxygen-initiated cascade reaction sequences. The amine groups do not react with singlet oxygen, but, instead, participate later on in the sequences that ultimately yield a diverse range of important alkaloid motifs. To illustrate the versatility of this chemistry, six natural products were synthesised very rapidly and efficiently. Furthermore, all the new technologies operated under green conditions and without the use of a single protecting group.

Chemoselective photooxygenations of furans bearing unprotected amines: their use in alkaloid synthesis.

Asymmetric and Site-Selective [3 + 2]-Annulations for the Synthesis of High-Value Bicyclic Lactams

4-Pyrrolin-2-ones are a lesser known tautomeric relative of the 3-pyrrolin-2-ones. Despite their infrequent appearance in the literature, they are very interesting and useful compounds. They have highly controllable, multisite and multitype reactivities which are covered in this review. The applications of these transformations show how the 4-pyrrolin-2-ones make excellent intermediates en-route to a range of key alkaloids. Innovative, fast and adaptable syntheses of the 4-pyrrolin-2-ones and their onward use via cascade reaction sequences are also presented to complete the case for commending these compounds as highly versatile and valuable synthetic building blocks.

/pdf/the-reticent-tautomer-exploiting-the-interesting-multisite-4kqurtiyhu.pdf

Manolis Sofiadis

Papers

Photooxygenation of Furylalkylamines: Easy Access to Pyrrolizidine and Indolizidine Scaffolds.

One‐Pot Transformation of Simple Furans into 4‐Hydroxy‐2‐cyclopentenones in Water

Chemoselective photooxygenations of furans bearing unprotected amines: their use in alkaloid synthesis.

Asymmetric and Site-Selective [3 + 2]-Annulations for the Synthesis of High-Value Bicyclic Lactams

The reticent tautomer: exploiting the interesting multisite and multitype reactivity of 4-pyrrolin-2-ones