The synthesis of the first polymer-supported TADDOL is reported. Its efficiency as chiral ligand of Ti(IV) was studied in the Diels-Alder cycloaddition of cyclopentadiene to 3-crotonoyl-1,3-oxazolidin-2-one, and was superior to that observed for its homogeneous equivalent, (4R,5R)-␣,␣,␣Ј,␣Ј-2-pentaphenyl-4,5-dimethanol-1,3-dioxolane. Recycling of the heterogeneous Ti(IV)-TADDOLate was also studied, being the most suitable method for the repreparation of the catalyst from the ligand after use. Chirality 9:191-197, 1997. © 1997 KEY WORDS: TADDOL; titanium complexes; chiral Lewis acid; polymer-supported; polystyrene-divinylbenzene; enantioselective; Diels-AlderThe Diels-Alder reaction is probably the most important synthetic method for obtaining cyclohexenes and is the key step in the synthesis of a large number of natural products.1 in the last few years, the asymmetric Diels-Alder reaction using chiral catalysts has been widely studied. [2][3][4] Especially interesting are the chiral Ti(IV) reagents derived from an achiral Ti(IV) Lewis acid and a 1,4-diol of general structure ␣,␣,␣Ј,␣Ј-tetraaryl-1,3-dioxolane-4,5-dimethanol 4,5 (TADDOL, Fig. 1). This family of compounds has proved to be an effective chiral catalyst not only in Diels-Alder reactions 6-8 but also in other types of reactions such as nucleophile addition to aldehydes, 4,9 enereaction, 10,11 [2+2] cycloadditions, 12 1,3-dipolar cycloaddition, 13 and hydrocyanation of aldehydes. 14 Very recently Greeves and co-workers 15 have reported the use of TADDOLs as chiral ligands for enantioselective addition of organocerium regents to aldehydes.Since the pioneering work of Merrifield 16 in solid-phase synthesis, much effort has been made in the development of new applications. Recently, attention has been focused in polymer-supported chiral catalysts because of the advantages implied: ease of chiral auxiliary isolation, ease of recovery and applicability in flow systems.Several polymeric chiral Lewis acids have been developed for asymmetric alkylations, [17][18][19] reductions, 20 or epoxidations, 21 but to our knowledge only Itsuno and coworkers 22 have synthesized effective polymeric chiral catalysts for enantioselective Diels-Alder reactions. These authors have studied the efficiency of several Nsulfonylamino acids, amino-alcohols, and diols anchored to an insoluble support as ligands of boron in the cycloaddition of cyclopentadiene to methacrolein, being 65% enantiomeric excesses (e.e.) 22a the best optical yield reached for the exo cycloadduct.Following our previous work on the enantioselective Diels-Alder reaction, 8 we report the synthesis of the polymer-supported TADDOL 1 (P-TADDOL, heterogeneous equivalent of (4R,5R)-␣,␣,␣Ј,␣Ј-2-pentaphenyl-4,5-dimethanol-1,3-dioxolane (2) (Fig. 2)), and its efficiency as a chiral ligand of Ti(IV) in the Diels-Alder addition of cyclopentadiene to 3-crotonoyl-1,3-oxazolidin-2-one. MATERIALS AND METHODS1 H-NMR spectra were recorded on a Varian-Gemini 300 spectrometer (Palo Alto, CA) at 300 MHz, in CDCl 3 , and ...

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