130 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 130–131 J. Chem. Research (M), 1997, 0879–0866 Novel Reactions of Methyl 4-(Triphenylarsoranylidene)but- 2-enoate and Substituted 2H-Pyran-5-carboxylates: the Preparation of Highly Functionalized trans- 2,3-Divinylcyclopropanecarboxylates Cornelis M. Moorhoff Department of Chemistry, University of Tasmania, GPO Box 252-75, Hobart, Tasmania, Australia 7001 Crotonate arsonium ylide reacted with 2H-pyran-5-carboxylates to give divinylcyclopropanecarboxylates. 2H-Pyran-2-carboxylates 13 have the unique character to undergo reversible electrocyclic ring opening to the ketodiene 2,5 making these compounds available for Michael attack (Scheme 1). In this paper we have investigated novel reactions of substituted 2H-pyran-5-carboxylates 1 and methyl 4-(triphenylarsoranylidene)but-2-enoate 3.7 A Ca–C3 Michael attack of 3 to 2 followed by ring closure and expulsion of triphenylarsine gave mainly highly functionalized trans-2,3-divinylcyclopropanecarboxylates 4 (Scheme 1).Likewise, 2H-pyran-5-carboxylates 1b and 1c gave a mixture of diastereomeric trans-2,3-divinylcyclopropanecarboxylates 4b and 4c. Cyclopropanation from conjugated carbonyl compounds with arsonium ylides is known.14 Vinylcyclopropanation from conjugated carbonyl compounds and arsonium ylides is less common.16 Both trans- and cis-2,3-divinylcyclopropanecarboxylates 4 show large vicinal coupling constants.21 Jvic(trans) was in the range 7.0–7.9 Hz, and Jvic(cis) between 8.6 and 9.3 Hz.Apart from a diastereomeric mixture of cyclopropanes 4c, the reaction of 3 and 1c gave cyclohexa-3,5-diene-1,3-dicarboxylate 6c. A Cg–C3-Michael attack of the g-ylide of 3 on 2c followed by an intramolecular Wittig condensation gave 6c (Scheme 2).2,22 The 2H-pyrans 1d and 1e reacted with 3 and gave, apart from the expected mixture of diastereomeric trans-cyclopropanecarboxylates 4d and 4e, the trans-fused tetrahydrobenzofurans 7d and 7e respectively.This is the result of an initial Cg–C5 Michael addition as illustrated (Scheme 3). Then an intramolecular Ca–C3 nucleophilic attack of the new intermediate arsonium ylide occurs. This is followed by an attack of the enolate oxygen on Ca with the simultaneous expulsion of triphenylarsine to give the tetrahydrobenzofuran 7. The formation of dihydrofuran compounds is rare in arsonium ylide chemistry.25 Techniques used: 1H NMR, 13C NMR, CI HRMS, IR, UV References: 25 Schemes: 6 Received, 14th November 1996; Accepted, 14th January 1997 Paper E/6/07733A Table Products arising from reactions of 2H-pyran-5- carboxylates 1 with methyl 4-(triphenylarsoranylidene)-but-2- enoate 3 2H-Pyran-5-carboxylate Product yields (%) 1 X R Rp 4 6 7 a bc def H Cl HH Cl Br Me Me Me HH Me OMe OMe SEt OMe OMe OMe 71 33 35 47 24 2 3 — 12 2 —— 98 Scheme 1 Scheme 2 Scheme 3J.CHEM. RESEARCH (S), 1997 131 References cited in this synopsis 2 C. M. Moorhoff, Ph.D. Thesis, University of Stellenbosch, 1986. 3 Zh. A. Krasnaya, E. P. Prokof’ev, V. F. Kucherov and M. Sh. Zaripova, Izv. Akad. Nauk. SSSR, Ser. Khim., 1973, 10, 2356 (Chem. Abstr., 1974, 80, 47772v). 5 T. A. Gosink, J. Org. Chem., 1974, 39, 1942. 7 Y.-Z. Huang, Y.-C. Shen, J. Zheng and S. Zhang, Synthesis, 1985, 57. 14 Y.-Z. Huang, Y.-C. Shen, Y.-K. Xin and J.-J. Ma, Sci. Sin. (Engl. Ed.), 1980, 23, 1396. 16 Y. Shen and Y. Xiang, J. Chem. Res. (S), 1994, 198. 21 (a) Y. Tang, Z.-F. Chi, Y.-Z. Huang, L.-X. Dai and Y.-H. Yu, Tetrahedron, 1996, 52, 8747. 22 For the phosphonium analogue, see: F. Bohlmann and C. Zdero, Chem. Ber., 1973, 106, 3779. 25 V. G. Kharitonov, V. A. Nikanorov, S. V. Sergeev, M. V. Galakhov, S. O. Yakushin, V. V. Mikul’shina, V. I. Rozenberg and O. A. Reutov, Dokl. Akad. Nauk SSSR, 1991, 319 (Chem. Abstr., 1992, 116, 83474v).