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Ligand-free 5-endo-dig cyclization of 1,4- and 1,2,4-substituted but-3-yn-1-yl (homopropargyl) azides in the presence of zinc chloride (usually 20 mol %) in dichloroethane at elevated temperature provides 2,5-di- and 2,3,5-trisubstituted pyrroles in high to moderate yields (91–41%). Both conventional and microwave protocols furnished comparable results. A structure of 2-(4-fluorophenyl)-5-(4-methylphenyl)-1H-pyrrole was confirmed by X-ray crystallography.

Conjugated polyalkynyl carbon chains, candidates for molecular wires, ( η 5 -C 5 Me 5 )Re(NO)(PPh 3 )(CC) n (Ph 3 P)(ON)Re( η 5 -C 5 Me 5 ) ( n =2 (Re*C 4 Re*), 4 (Re*C 8 Re*), 6 (Re*C 12 Re*)), have been deposited as thin films on air passivated copper surfaces and examined by X-ray photoelectron spectroscopy before and after exposure to air for various periods of time. The reactivity patterns of these thin films have been determined by examination of the oxidation state of Re and the chemical states of carbon, oxygen and phosphorus. Rhenium, which is zero valent in the starting compounds (Re*C 4 Re*), (Re*C 8 Re*) and (Re*C 12 Re*) reacts to form Re 3+ , Re 4+ and Re 5+ . Their thin film reactivities will be discussed and compared to their solution electrochemistry. We have found Re*C 4 Re* and Re*C 8 Re* to be more reactive than Re*C 12 Re* in agreement with the cyclic voltammetry results.

The diyne (η5-C5Me5)Re(NO)(PPh3)(CCCCSiMe3) is elaborated to (η5-C5Me5)Re(NO)(PPh3)(CCCCCCSiR3) (R=Me, 3a; Et, 3b) by sequences involving n-Bu4N+F− in aqueous THF to give (η5-C5Me5)Re(NO)(PPh3)(CCCCH) (91%), n-BuLi/CuI or t-BuOCu to give (η5-C5Me5)Re(NO)(PPh3)(CCCCCu) (4), and coupling with ICCSiMe3 (48%) or BrCCSiEt3 (84–65%). Complex 3b is similarly converted to (η5-C5Me5)Re(NO)(PPh3)(CCCCCCH) (88%) and (η5-C5Me5)Re(NO)(PPh3)(CCCCCCCu) (6). Reactions of 4 and 6 with BrCC-p-C6H4Me give the title compounds (η5-C5Me5)Re(NO)(PPh3)((CC)n-p-C6H4Me) (n=3, 7; 4, 8; 77–66%). Optimized one flask conversions of 1a and 3b to 7 (81%) and 8 (71%) are described. The crystal structures of 7 (monoclinic, P21/c, a/b/c=17.951(8)/8.377(5)/22.160(9) A, β=103.63(5)°, Z=4), and 8 (monoclinic, P21/n, a/b/c=8.426(3)/16.400(6)/25.400(9) A, β=97.51(3)°, Z=4) show markedly curved sp carbon chains—much more than hexatriynes or octatetraynes reported to date. The bond angles associated with the Re(CC)nC moieties (min/max/avg) are 169.1(10)°/178.8(13)°/174.7° (7) and 170.0(9)°/178.8(10)°/175.7° (8). Other structural features are normal, and bending is provisionally ascribed to packing forces. Reaction of 7 and HBF4·OEt2 gives the cationic vinylidene complex [(η5-C5Me5)Re(NO)(PPh3)(CC(H)CCCC-p-C6H4Me)]+BF4−, the structure of which is established by extensive NMR analyses.

The reaction of readily available dialkyltrimethylsilyl phosphites (RO)2POSiMe3 5 with sulfur dichloride leads to tetra-alkyl sym-monothio-pyrophosphates (RO)2P(O)SP(O)(OR)2 1 in high yield. The method is suitable for the synthesis of tetra t-butyl thiopyrophosphate 1d.

3,4',5,7-tetraacetyl quercetin (1) was isolated from the heartwood of Adina cordifolia. The structure was elucidated on the basis of spectral evidence.