This account intends to cover recent literature on photoinduced substitution reactions in water or aqueous media with synthetic utility.Interesting synthetic targets, such as benzothiazine rings, benzoxazoles, aromatic photosubstitutions on 6-fluoroquinoles, can be accomplished in a benign aqueous environment, reducing the impact of organic solvents, or the use of metals for substitution reactions.Synthetically-useful electron-transfer substitution reactions performed in aqueous media are noteworthy and not much developed. These reactions performed either through radicals or radical ion intermediates generated photochemically in aqueous environment will prove convenient and alternative sustainable options at hand for the organic synthetic chemist. Metal-mediated photoinduced electron transfer reactions will not be dealt with in this account, as have been the subject of recent review articles, as is the case of radical perfluoroalkylation substitution reactions in aqueous media which have been recently summarized.Keywords: Photocyclization in aqueous media, PET-in aqueous media, Photosubstitution in aqueous media.Radicals and radical ion species in organic synthesis have been invoked increasingly during the last two decades accounting for many methods of carbon-carbon bond formation. Thus, carboncarbon bond formation via carbon-centered radicals or through photoinduced electron transfer reactions (PET) is regarded as a useful choice available to the synthetic chemists. These routes have the advantage of tolerating the presence of water, and therefore reducing the environmental impact on synthesis. In this class of reactions, photoinduced addition and substitutions play important synthetic roles. For more than a century, carbon-carbon bond formation in aqueous media has been virtually limited to electrochemical processes and aldol condensation reactions. Using radicals and radical ions in water or a water-containing mixed solvents reduces the use of toxic or dangerous environments, simplifies the work-up (often a simple extraction), and takes advantage of the specific effects occurring in water, such as hydrogen-bonding. Only very recently were radicals employed in the formation of carboncarbon bonds in aqueous media [1]. Such reactions were usually carried out through some modification of the usual methods of generation of radicals e.g. through hydrosoluble initiators, the Et 3 B/O 2 method and H 3 PO 2 as the reducing agent. Also, (Me 3 Si) 3 SiH was recently used in water, proving an excellent H-donor in this medium [1]. In some of the latter experiments the chemical yields in water were better than in an organic solvent.Radical substitution reactions in aqueous environment employing metallic species have been recently reviewed [2,3]. Electrontransfer substitution reactions in aqueous media have also been recently discussed in the literature [4]. However, syntheticallyuseful electron-transfer photosubstitution (PET-substitution) reactions performed in aqueous media are noteworthy and not much developed.This acco...

This account intends to cover recent literature on photoinduced cyclization reactions in water or aqueous media. The reactions covered do not proceed by the assistance of metals, or through electron transfer reactions mediated by metallic species or complexes. Radical cyclization of perfluoroalkyl-substituted compounds is neither the subject of this article, since these examples have been reviewed recently. Instead, photomacrocyclization and photoelectrocyclic ring closure reactions are the aims of this article, as well as the syntheses of lactones and 5-methyleneoxazolidin-4-ones, showing the scope of these reactions carried out in an environmentally-friendly media. These cyclization reactions will be shown to enable the syntheses of important synthetic targets, with relevancy in biochemistry and medicinal chemistry.