INTRAMOLECULAR COUPLING REACTIONS OF ALLYLIC THIOESTERS WITH DIENE IRON TRICARBONYL SYSTEMS

Cyclization reactions are reported for a series of allylic thioester d erivatives of cyclohexadiene iron tricarbonyl systems, leading to the formation of spiro thialactone derivatives. The overall reaction proce ss is equivalent to a [6 pi + 2 pi] ene reaction in which the pendant alkene, derived from the allyl thioester, is coupled with the diene of the diene-Fe(CO)(3) moiety. While simple substrates were found to und ergo this cyclization readily, increased substitution on the pendant d ouble bond led to lower, or zero, yields. Methodology for ring opening of the product thialactones, with or without reductive extrusion of s ulfur, is described. The X-ray structure of one of the products (21b) is reported: C15H14FeO4, M-r = 346.17. Crystal dimensions: 0.20 x 0.20 x 0.10 mm: Yelow, clear prism. Mo K alpha radiation (lambda = 0.71073 Angstrom). Monoclinic space group P2(1)/n; alpha = 11.355(2) Angstrom , b = 6.4943(13) Angstrom, c = 20.060(4) Angstrom, beta = 103.30(3)deg rees, V = 1439.6 (5) Angstrom(3). Z = 4. Theta = 2.35-27.06 degrees. T = 150 (2) K.