TETRAHEDRON LETTERS Pergamon Tetrahedron Letters,40 (1999) 3899-3902 Mo(CO)6/TBHP Catalyzed Autoxidation of 5-Alkylidene-4,5-Dihydrofurans Alessandra Lattanzi*, Patrizia Iannece and Arrigo Scettri Dipartirnentodi Chimica,Universit~ degli Studi di Salerno,84081 Baronissi(SA), Italy Received 1 February 1999; accepted 15 March 1999 Abstract: Mo(CO)6/t-butyl hydroperoxide, well known to epoxidizeolefins, was shown to be a mild and very efficient system for the autoxidation of 5-alkylidene-4,5-dihydrofurans. High yields of primary, secondaryand tertiary furyl hydroperoxides have been achievedemploying catalytic amount of Mo(CO)6. A radical mechanismis in agreementwith the experimental data. © 1999 Elsevier ScienceLtd. All rights reserved. Epoxidation of olefms represents one of the fundamental processes in preparative organic synthesis. 1 Early transition metal compounds (e.g., Mo, Ti, W and V), in combination with hydrogen peroxide or alkyl hydroperoxides, can be considered the most popular catalytic systems) In particular, soluble molybdenum compounds satisfy the requirements to be active and selective epoxidation catalysts. In fact, they act as strong Lewis acids (Scheme 1) increasing the electrophilic character of the peroxidic oxygens and, furthermore act as weak oxidants in their highest oxidation state. This reduces the competing one electron oxidation of the ROO Mn/O-,,O_R Mn--O--R + ~ - (1) / Mn/O'-.O__R . M n'l + RO0" (2) ligand3 (Scheme 1, eq. 2). 2 ROO" . 2 RO" + 02 (3) Scheme 1 A set of preliminary experiments, performed on 5-alkylidene-4,5-dihydrofurans 4 of type 1 pointed out a different behaviour of the Mo(CO)6-TBHP catalytic system. Under the conditions reported for the representative starting compound la (R=Et, RI=R2=Me, R3-H, Scheme 2, Table 1) the formation of hydroperoxide s 3 proved to be the favoured process. o R Mo(CO)6 ~ R3 . K ~ R2 C6H6, T 8 I ~ + I | ~" I 1 R2 [ 2 R2 ] 3 OOH Scheme 2 0 R O ~ R3 + Rl,//~O/~ R 2 4 OH * Correspondingauthor. E-mail: lattanzi@ponza.dia.unisa.it 0040-4039/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S0040-4039(99)00564-X