A New Environmentally Benign Catalytic Process for the Asymmetric Synthesis of Lactones: Synthesis of the Flavouring d-Decalactone Molecule Avelino Corma a, *, Sara Iborra a , MarÌa Mifsud a , Michael Renz a , Manuel Susarte b a Instituto de TecnologÌa QuÌmica, UPV-CSIC, Avda. de los Naranjos s/n, 46022 Valencia, Spain Fax: (  34)-96-387-7809; e-mail: acorma@itq.upv.es b Acedesa-Takasago, Murcia, Spain Received: December 17, 2003; Accepted: February 7, 2004 Abstract: The system Sn-Beta/hydrogen peroxide is applied to the Baeyer±Villiger oxidation of delfone to d-decalactone, which is an industrial fragrance. The reaction is carried out without solvent and with a substrate/catalyst ratio > 200 (wt/wt). Starting with an enantiomerically enriched delfone it is shown that the rearrangement occurs with retention of configuration at the migrating asymmetric carbon atom, and enantiomerically enriched d-decalactone is obtained as product. This process offers clear advantages over the actual industrial production that uses peracids as oxidants. Keywords: Baeyer±Villiger oxidation, d-decalactone, heterogeneous catalysis, hydrogen peroxide, tin, zeo- lites Introduction Lewis acids have been used for a long time to catalyse selective oxidations. [1] An important breakthrough in thedesignofheterogeneousoxidationcatalystswasthe discovery of Ti-silicalite (TS-1). [2] Titanium was incor- poratedintheframeworkofsilicalitezeoliteasisolated tetrahedralTi(IV)sites.Thesemetalcentresareableto form titanium-peroxy species and, thereby, to activate hydrogen peroxide for oxidation reactions such as epoxidation, ammoximation or CH oxidation. [1] Inthecourseoftheexcitingoxidationchemistrywith TS-1, other metals have been incorporated into mo- lecular sieves, such as vanadium, chromium, zinc, iron, and tin, the latter with an increasing number of applicationsinrecentyears.Severalpatentsandreports have appeared on the hydroxylation of phenol with Sn- silicalite, [3] Sn-MCM-41 [4] and tin incorporated in other zeolite structures. [5] However, when the results are compared with titanium incorporated into the same molecular sieve the titanium-containing materials al- ways perform better [3b] or much better. [6] Sn-Beta however, was found to be particularly active for Meerwein±Ponndorf  Verley and Oppenauer reactions in which carbonyl groups are reduced and alcohols are oxidised. [7] With respect to epoxidation only the oxida- tion of the very reactive norbornene has been reported with tert-butyl hydroperoxide as oxidant and Sn-MCM- 41ascatalyst,whileSn-Betawasfoundtobeabsolutely inactive for epoxidation reactions with hydrogen per- oxide. [8,9] These results indicate that tin-containing molecular sieves are less effective catalysts for the activationofhydrogenperoxideforoxidationreactions. Inspiteofthelackofactivityforaneffectivehydrogen peroxide activation, we have presented recently a very chemoselective oxidation reaction with hydrogen per- oxide catalysed by Sn-Beta, [8,10] namely the Baeyer± Villiger oxidation. This is an important reaction for organic synthesis which finds many applications in the finechemicalindustry. [11] Ithasbeendemonstratedthat thewater-resistantheterogeneousLewisacidSn-Betais abletoactivatethecarbonylgroupofcyclicketonesand aromatic aldehydes for the nucleophilic attack of hydrogen peroxide to give the corresponding Baeyer± Villiger reaction products. [8b,12] In the case that double bonds were present in the substrate molecules, no epoxidation was observed in contrast to reactions with other classical oxidants such as peracids or MTO/H 2 O 2 . With tin incorporated into the mesoporous molecular sieve MCM-41 during synthesis or in a post-synthesis treatment, two materials were available without the limitation of molecular size introduced by the pores of the Beta zeolite (6.2±7.2 ä). [13] By insitu IR spectro- scopy it was established that Sn-Beta has the highest Lewis acid strength of the three materials so that substrates that were able to diffuse within both channel systems without steric impediments were oxidised fastest in the presence of Sn-Beta. These insitu IRmeasurementsprovidedalsovaluable information for the proposal of a catalytic cycle. By the coordinationofthecarbonylgrouptotheSnLewisacid site, the corresponding IR band of the C  O group is FULL PAPERS Adv.Synth.Catal. 2004, 346,257±262 DOI: 10.1002/adsc.200303234 ¹ 2004 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim 257