Journal of Photochemistry and Photobiology A: Chemistry 185 (2007) 38–43 Synthesis and photochemical reactivity towards the Patern´ o–B¨ uchi reaction of benzo[b]furan derivatives: their use in the preparation of 3-benzofurylmethanol derivatives Maria Capozzo, Maurizio D’Auria ∗ , Lucia Emanuele, Rocco Racioppi Dipartimento di Chimica, Universit` a della Basilicata, Via N. Sauro 85, 85100 Potenza, Italy Received 25 February 2006; received in revised form 18 April 2006; accepted 9 May 2006 Available online 17 May 2006 Abstract 4-Amino-2,7-dimethylbenzo[b]furan and 4-chlorobenzo[b]furan have been synthesized. The irradiation of 4-amino-2,7-dimethylbenzo[b]furan in the presence of benzaldehyde gave the corresponding endo adduct. The adduct can be hydrolysed to the corresponding 3-benzofurylmethanol derivative. The irradiation of the same compound in the presence of benzophenone gave the corresponding adduct. 4-Chlorobenzo[b]furan did not react with benzaldehyde while, in the presence of benzophenone, gave the corresponding adduct. The hydrolysis of this adduct gave the corresponding 3-benzofurylmethanol derivative. © 2006 Elsevier B.V. All rights reserved. Keywords: Benzofuran derivatives; Photochemistry; Patern` o–B¨ uchi reaction 1. Introduction The Patern` o–B¨ uchi reaction is a photochemical [2 + 2] cycloaddition reaction between a carbonyl compound and an alkene. Recently we reported some applications of the Patern` o–B¨ uchi reaction on furan derivatives in the realization of diastereoselective syntheses [1–10]. We showed that the pres- ence of a hydroxyl group on the side chain on the furan ring can induce a high diastereoselectivity when the reaction is performed in the presence of benzaldehyde or benzophenone. Furthermore, diastereoselective reaction can be obtained if the carbonyl com- pounds used in the reaction have a chiral auxiliary (i.e. the alcoholic part of an ester) in the structure, or if the carbonyl com- pounds are chiral (i.e. -hydroxyketones). The Patern` o–B¨ uchi reaction on furan has been used in the past in the synthesis of sev- eral biological active natural compounds, such as perillaketone, asteltoxin, oxetanocin, and avenaciolide [11,12]. The possible use of substituted benzofuran derivatives in the treatment of osteoporosis (1) [13,14], as anaesthetic agent (2) [15,16], as inhibitors of platelet aggregations (3) [17], as ∗ Corresponding author. Tel.: +39 0971 202240; fax: +39 0971 202223. E-mail address: dauria@unibas.it (M. D’Auria). inhibitors of xanthyn oxydase (4) [18], as antiarrythmycs (5) [19], as anti-HIV agents (6) [15], as agonist of the benzodi- azepines [20], as inhibitors of ATPase (1) [21] has been described (Fig. 1). Most of these compounds are benzofuran derivatives substi- tuted in position 3 with a side chain containing in  position an alcoholic function or a carbonyl group. The Patern` o–B¨ uchi reaction has been performed on benzo- furan [7,22,23] but no synthetic use of reaction was described. Furthermore, the acid treatment of the oxetanes obtained in the reaction between ketones and furan derivatives converted them into 3-furylmethanol derivatives [24–26] (Scheme 1), but the use of this methodology on the oxetanes obtained from benzo- furan derivatives does not seem to have large synthetic utility. In fact, the use of treatment of the oxetanes obtained from the reaction between benzofuran and 1-acetylisatine gave a mix- ture of products, where chloro substituted dihydrobenzofuran derivatives were present [27]. In this paper we want to report the results of our study devoted to improve the synthetic utility of the Patern` o–B¨ uchi reaction on benzofuran derivatives: our goal was to obtain compounds with a structure similar to that of the biologically active compounds described above. Here we describe the synthesis of suitable benzofuran derivatives, the results of the oxetane formation reaction of these substrates and 1010-6030/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jphotochem.2006.05.007