Aromatic compounds => diynes

Various acetylenes having functional groups such as halide, alcohol, ether, amine, alkene and nitrile, are tolerated in the reaction. An asymmetric (2+2+2) cydoaddition of a,03-diynes with alkyne was achieved by a [IrCl(cod)]2 catalyst combined with a chiral phosphine ligand such as MeDUPHOS and EtDUPHOS, and gave axially chiral aromatic compounds [20]. 

The reaction of a,co-diyne with monoene instead of monoyne also gave an aromatic compound (Scheme 5.4) [9], The reaction included cleavage of a C—O bond. Diyne 7 reacted with 50 equiv of 2,3-dihydrofuran to give aromatic alcohol 8 in 97% yield. Acyclic vinyl ether such as n-butyl vinyl ether could be used in place of 2,3-dihydrofuran. The reaction of 7 with 25 equiv of n-butyl vinyl ether gave 9 and 10. The combined yield was nearly quantitative. n-Butyl vinyl ether acted as an acetylene equivalent when the reaction gave 9. Based on this result, an enol ether could be used as an acetylene equivalent in Rh-catalyzed [2 -j- 2 -j- 2] cycloaddition [11]. 

Cook and co-workers took advantage of the molybdenum-based methodology and reported one of the most graceful applications of the allenic PKR. They intended to use PKR to synthesize a theoretically interesting tetracyclic compound 55, which has 14 vr-electrons and is supposed to be aromatic in principle. To this end, they have applied PKR to various alkynyl allenes, and finally employed a diyne-diallene substrate 54 successfully (Equation (27)). Double PKR by employing molybdenum hexacarbonyl in excess and DMSO afforded the requisite intermediate in a high yield. 

Phase-transfer catalysis is a useful procedure for a variety of interesting metal-catalyzed reactions. - However, only one example of this approach has been reported for the synthesis of diynes by the sp-sp carbon coupling reaction. Thus vinylic dibromides derived from aromatic aldehydes have been shown to react with carbon monoxide, in the presence of zerovalent palladium compounds as the metal catalyst, and under phase-transfer conditions in a two-phase system (benzene, 5 M NaOH), to give the corresponding diynes in reasonable yields (equations 21 and 22). ... 

Hexadehydro-[ 18]annulene 80>, 15, (see Table 4) possesses no inner protons and the six equivalent outer protons resonate at t 2.98. This represents a downfield shift of over 1 ppm from a model compound, cis-hex-3-ene-l,5-diyne, 9, (t 4.11). This model compound also served to clarify the interpretation of the singlet at t 5.55 in the case of l,5,9-tridehydro-[12]annulene, 1, a molecule for which aromaticity is not predicted. The downfield shift of 15 and the upfield shift of 1 from the acyclic model can then be attributed to a diamagnetic ring current in 15 and a paramagnetic ring current in 1. 

Axially chiral biaryls are found widely in the key structure of useful chiral ligands and catalysts [1] and biologically active compounds [2], The conventional method for their catalytic asymmetric synthesis is based on an asymmetric cross-coupling approach [3], As a conceptually new approach to axially chiral biaryls, asymmetric aromatic ring construction via transition-metal-catalyzed [2 - - 2 + 2] cycloaddition has recently appeared [4], In 1999, Sato et al. reported two types of nickel-catalyzed [2-1-2-1-2] cycloaddition for the synthesis of functionalized biaryls [5], One was the cycloaddition of aryl-substituted monoyne 1 with acetylene, leading to biaryl 2 (Scheme 9.1), and the other was the cycloaddition of aryl-substituted 1,6-diyne 3 with acetylene, leading to biaryl 4 (Scheme 9.2) [5],... 

The reaction of zirconacyclobutene-silacyclobutene fused compound 46 formed from Si-tethered diyne 45 with Cp2Zr(II) species has been used in the synthesis of fused aromatic heterocycles 47 (Scheme 11.18) [20]. When the zirconacycles 46 reacted with nitriles, the corresponding pyrrolo[3,2-c]pyridines 47 were formed. This indicates the unexpectedly strong effects of the alkynylsilyl groups on this unusual skeletal rearrangement of zirconacycles. 

The concept of their homologation method is outlined in Scheme 11.34. Starting from the 3,4,5,6-tetraalkylphthalates 6, reduction and bromination of two ester groups, alkynylation of the resulting dibromides 87, zirconium-mediated cyclization of diynes 88 with dimethyl acetylenedicarboxylate and subsequent aromatization by DDQ (2,3-dichloro-5,6-dicyano-l,4-benzoquinone) afforded the anthracene derivatives 91 in six steps. Tricyclic compounds 91 thus formed are also substituted phtha-late derivatives, which are the same as 86. The tricyclic skeleton of 91 can again be extended to pentacyclic compounds 92 by the same combination of procedures as for 86 [35],... 

---