In the reaction of Fe(CNR)3(t'-Pr-a-diimine) (6; R = 2,6-xyIyl (a), t-Bu (b), c-Hex (c)) with dimethyl maleate, two totally different pathways are followed, depending on the type of isocyanide used. With the aromatic isocyanide, a 1,3-dipolar cycloaddition of the alkene to the Fe-N=C unit occurs followed by an isocyanide insertion, forming a ferra [2.2.2] bicyclic compound (7a). When this mixture is warmed above room temperature, the reaction is reversed, disassembling 7a into its starting components. During this facile retro-cycloaddition, C-C, C-N, and Fe-C bonds are broken. Also, the first unambiguous example of an isocyanide deinsertion is encountered. The starting complexes 6b,c, with aliphatic isocyanides, react with dimethyl maleate to give two products. The first, a purely organic product (8), is a dimer of two coupled alkenes. The second product is the organometallic tricyclic complex FeiCNRMtric) (9b,c), in which two alkenes are coupled and bonded to the metal and the -diimine ligand. In the cyclization reaction, a -lactam ring is formed and a methoxy group of one of the four ester groups is removed, with formation of methanol. The molecular structure of the [2.2.2] bicyclic complex 7a (FeCeoHgoNeO*, triclinic, space group , a = 10.367 (1) A, b -14.615 (3) A, c = 15.787 (2) A,a = 95.78 (2)°, ß = 96.62 (1)°, y = 92.21 (1)°, Z = 2,R = 0.053, Rv = 0.055) consists of three six-membered rings with the metal in a bridgehead position. The single-crystal X-ray structure of the organic dimer 8 (CizHigOg, monoclinic, space group A2/o, a = 8.291 (2) A, b = 8.291 (2) A, c = 20.551 (2) A, ß -96.09 (1)°, Z = 4, R = 0.068, Rw = 0.089) reveals a symmetric alkene. The molecular structure of the Fe(i-BuNC)3(tric) species 9b (FeCsiHssNsOv-O.SCIL-CI2O.5C4H10O, monoclinic, space group Pc, a = 11.201

The preparation of d,l-phenylalanine via amidocarbonylation of benzyl chloride with acetamide and CO/H(2) is described. The rate of the reaction is dependent upon the CO pressure below 250 bar, but independent of the hydrogen pressure. A reaction temperature of 100 degrees C gives optimum yields. A relatively large amount of the catalyst, Co(2)(CO)(8), is needed for complete conversion because of inhibition caused by hydrogen chloride which is formed during the reaction. Addition of NaHCO(3) removes HCl as insoluble NaCl, resulting in improved conversion and selectivity of the reaction. It also allows the use of a stoichiometric amount of acetamide, whereas a 2- to 3-fold excess of acetamide is needed for complete conversion of benzyl chloride without NaHCO(3). Amidocarbonylation of benzyl alcohol gave d,l-phenylalanine in only 8% yield.

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1993organo-iron compounds organo-iron compounds S 7100 -2481,3-Dipolar Cycloaddition to the Fe-N=C Fragment.Part 11. Isocyanide-Controlled Change Between a Reversible Molecular Self-Assembly of Three Components, Including a Unique Isocyanide Deinsertion, and Dimethyl Maleate Coupling Reactions.-The complexes (I) and (IV) react with the alkene (II) depending on the type of isocyanide used by two different routes for which the mechanisms are discussed. With the aromatic isocyanide the bicyclic compound (III) is formed, a process which can be reversed at higher temperature. With aliphatic isocyanides the tricyclic complexes (V) are obtained besides the purely organic product (VI). The structures for (III), (Va) and (VI) are determined by X-ray analysis. -(DE LANGE, P. P. M.; DE BOER, R. P.; VAN WIJNKOOP, M.; ERNSTING, J. M.; FRUEHAUF, H.-W.; VRIEZE, K.; SMEETS, W. J. J.; SPEK, A. L.; GOUBITZ, K.; Organometallics 12 (1993) 2, 440-453; J. H. van't Hoff Inst., Univ. Amsterdam, 1018 WV Amsterdam, Neth.; EN)