Russian Chemical Bulletin, International Edition, Vol. 51, No. 3, pp. 526—530, March, 2002 526 1066-5285/02/5103-526 $27.00 © 2002 Plenum Publishing Corporation Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 489—492, March, 2002. Chemistry of Natural Compounds, Bioorganic, and Biomolecular Chemistry Synthesis of chromenes with isoprenoid side chains and their selective ozonolysis V. N. Odinokov,  A. Yu. Spivak, G. A. Emel´yanova, and B. I. Kutepov Institute of Petrochemistry and Catalysis, Bashkortostan Republic Academy of Sciences and Ufa Scientific Center of the Russian Academy of Sciences, 141 prosp. Oktyabrya, 450075 Ufa, Russian Federation. Fax: +7 (347 2) 31 2750. E-mail: ink@anrb.ru The reactions of trimethylhydroquinone with isoprenoid allylic alcohols catalyzed by a Pentasil type zeolite in the H-form gave trimethyl-1,4-benzoquinones with the corresponding isoprenoid group, which were subsequently transformed into the target Δ 3 -chromenes on treatment with pyridine. Partial ozonolysis of chromenes proceeded selectively at the Δ-bond of the side chain, resulting in the corresponding chromenes with an ω-carbonyl group. Key words: 1,4-benzoquinones, Δ 3 -chromenes, isoprenoids, allylic alcohols, hydroquinones, zeolites, ozonolysis, aldehydes. Chromenes with isoprenoid side chains are frequently encountered in nature, being structural analogs of prenyl- ated coumarins, chalcones, and cannabinoids; 1—3 this ac- counts for the enhanced interest in the synthesis of these compounds. Two approaches have been developed most thoroughly, namely, (1) an approach using the pyridine- catalyzed reaction of α,β-unsaturated aldehydes with phenols 4 and (2) a two-step route comprising the reaction of trimethylhydroquinone (TMHQ) with tertiary allylic alcohols to give prenylated 1,4-benzoquinones and sub- sequent cyclization of these compounds induced by pyri- dine. 5 Alkylation of TMHQ with allylic alcohols cata- lyzed by Lewis acids (usually ZnCl 2 or BF 3 •OEt 2 ) is the key step in the latter method. We synthesized prenylated 1,4-benzoquinones using a heterogeneous zeolite of the Pentasil type in the H-form. Unlike the zeolite-containing Tseokar-10 catalyst, which we used in the synthesis of α-tocopherol and its ana- logs, 6,7 the Pentasil catalyst is less active because the concentration of the acidic active sites on its surface is lower. 8 The reactions of TMHQ with linalool (1) and a 1 : 1 mixture of (3R,4S)- and (3S,4S)-3,4,8-trimethylnona- 1,7-dien-3-ols (2) (ee ∼50%) in the presence of Pentasil were found to afford 1,4-benzoquinones 3 and 4, respec- tively. Pyridine-induced cyclization of these products pro- ceeded smoothly to give chromene 5 and a mixture of chromene 6 diasteromers, respectively.