The conversion of cyclic diketones 1 and 3 into the corresponding dibromoalkenes 2 and 4 via Corey-Fuchs procedure is described. Subsequent alkynylation of 2 and 4 as well as 9-(dibromomethylene)fluorene (6) yields the geminal enediynes 5a-e , 7a-e , and 8a-c .The cyclohexane backbone of 5a,d can be oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to the p -quinoid systems 9a,b .In our earlier work, 1, 2 we have explored the syntheses of peri-ethynyl substituted 1,6-methano[10]annulene derivatives and investigated the interactions between their acetylene fragments. Several multi-ethynyl substituted derivatives were synthesized and the properties of these and other isolated products were investigated; we have also synthesized some enediyne units as derivatives of 1,6-methano[10]annulenes using palladium-catalyzed cross coupling reactions. 1,2 Enediyne units can also be substructures in molecules designed to serve as precursors to two-dimensional carbon networks. 3 Very often, substances of this type are made up of tetraethynylethene building blocks. 4 Carbon networks prepared from this type of molecules would have distinctive physical properties; selective substitution of the monomeric starting materials with cyclic aliphatic or aromatic saturated or polyunsaturated groups could probably significantly change the physical properties of the resulting polymeric carbon networks.In order to prepare suitable precursors for such novel all carbon networks, we chose to transform cyclohexane-1,4-dione (1) and anthraquinone (3) into the corresponding dibromoalkenes (Schemes 1 and 2). These dibromoalkenes as well as the known fluorene derivative 6 5 (Scheme 4) should represent suitable starting materials for catalytic alkynylation yielding novel cyclic geminal enediynes.According to known literature procedures, 6 the ketones 1 and 3 were reacted with CBr 4 /PPh 3 mixtures in anhydrous benzene. After reaction at room temperature for 15 and 10 hours, respectively, the dibromoalkenes 2 and 4 could be isolated by filtration of the reaction mixtures, evaporation of the filtrates and column chromatography on silica gel in yields of 93% for 2 and 36% for 4 . Dibromoalkenes 2 and 4 are colorless solids that are stable to air at ambient temperature and melt at 140-145°C (subl. ) and 73°C, respectively.Besides these two dibromoalkenes, 9-(dibromomethylene)-9 H -fluorene 5 (6) was chosen as an interesting starting material for alkynylations. 7 Substitution of bromine atoms in 2 , 4 , and 6 was achieved by using different palladium catalysts, namely, Pd(PPh 3 ) 4 , Pd(PPh 3 ) 2 Cl 2 and Pd(PhCN) 2 Cl 2 . No systematic relation between the structure of the dibromoalkenes or the type of alkyne and the best suited catalyst was observed; instead, the optimum catalyst for a given reaction was found by comparison between several runs under different conditions. Reactions were conducted in anhydrous benzene at temperatures between room temperature and 80°C. For elimination of the HBr formed during the substitution reactions, variou...

The chiral cluster (2,4,6-But3C6H20)P-Fe(CO)(q5-C5Me5)-(p2-CO)-Fe(CO)3Mn(C0)4 6 has been synthesized stepwise from (R)(q1-C5Me5)P=Mn(C0)4 1 (R = 2,4,6-But3C6H20) and Fe2(CO)9 2; the rearrangement of q2-{ (R)(ql-C5Me5)-P=Mn(C0)4}Fe(C0)4 3 to (R)[(q5-C5Me5)Fe(CO)2]P=Mn(C0)4 4 proves to be the decisive step in this synthesis; the X-ray structure analysis of 4 and 6 are reported.There is wide interest in chiral heterometallic clusters.' The synthesis of these type of compounds can be achieved most commonly by exchange of organometallic building blocks in non-chiral clusters2 or addition of new organometallic fragments to unsaturated organometallic compounds.3We recently described the synthesis of the bifunctional complex (R)(q1-C5Me5)(P=Mn(CO)4 1 (R = 2,4,6-But3-C6H20) .4 This compound contains two potential coordination sites (the P=Mn double bond unit and the ql-CsMeS fragment) for coordinatively unsaturated organometallic building blocks. Addition of various organometallic fragments to 1 is expected to result in the formation of chiral clusters.Here we describe the stepwise synthesis of the chiral cluster (R)P-Fe(CO)(q5-C5Me5)-(p2-CO)-Fe(CO)3-&in(CO)4 6 by the reaction of (R)(q*-C5Me5)P=Mn(C0)4 l4 with Fe2(C0)92.

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