A,co-Diynes

Homogeneous, single-component catalysts such as, e.g., W(=CCMe3)(OCMe3)3 or W(=CMe)(OCMe2CF3)3, cannot only be used for exchange metathesis of alkynes but also for ROMP of cycloalkynes, ADMET of a,to-diynes, and RCM of a,co-diynes [751]. 

The catalytic intramolecular coupling of two C=C bonds at a ruthenium site leads to cyclization reactions. For example, although generally less reactive than a,co-diynes or enynes, 1,6-dienes react with [RuC12(COD)] in 2-propanol, leading to exo-methylenecyclopentanes in excellent yields [13] (Eq. 8). The mechanism suggests the formation of the ruthenacyclopentane(hydrido) intermediate 19. 

Related cyclocotrimerizations of two alkyne molecules with isocyanates have also been achieved using cobalt and nickel catalysts [9], With respect to intramolecular versions, two examples of the cobalt(I)-catalyzed cycloaddition of a,co-diynes with isocyanates have been reported to afford bicyclic pyridones only in low yields, although 2,3-dihydro-5(lH)-indolizinones were successfully obtained from isocyana-toalkynes and several silylalkynes with the same cobalt catalysis [50], On the other hand, the cycloaddition of 1,6-diynes 20 with 4 equiv. of isocyanates proceeded in refluxing DCE under the ruthenium catalysis to afford bicyclic pyridones 58 in 58-93% yield (Scheme 4.21) [51], Both aryl and aliphatic isocyanates can be widely employed in this pyridone annulation. 

Misumi and his coworkers have prepared 1,3-cycIotetradecadiyne (14S) and 1,3-cyclotridecadiyne (146) by Eglinton s oxidative coupling under high dilution conditions of the corresponding a,co-diynes - . 1,3-Tridecadiyne (146), the smallest... 

These dimerisation reactions of terminal alkynes have been further extended to the catalytic cyclisation of a,co-diynes. For example, treatment of 1,15-hexa-decadiyne with 10 mol% of 7a affords the endo-msLCTOcydic product, (Z)-l-cyclohexadecen-3-yne with complete stereoselectivity (Equation 5). This novel cyclisation is of particular utility, because synthetic routes to endo-cyc ic (Z)-l-en-3-ynes are extremely limited. A related palladium-catalysed cyclisation of a,co-diynes to give the corresponding exo-cyc c l-en-3-ynes has been reported by Trost and co-workers. 

Likewise, a,co-diynes can be used in this cycloaddition for instance, octa-l,7-diyne 176 affords the 5,6,7,8-tetrahydroisoquinoline 177 with nitriles ... 

Isoindolines and isoquinolines a,co-Diynes in which the connecting chains contain a nitrogen atom undergo [2+2+2]-cycloaddition with ketene equivalents derived from the carbene complexes. After the formation of a benzene ring, the products are isoindoline or isoquinoline derivatives. 

Reviews on cyclic diacetylenes and on transition-metal-catalysed cyclizations of a,co-diynes 646 (e.g. equation 65) have appeared. 

Hydroboration of a,co -diynes with boron tribromide yielded (equation 43) a novel type of organoborane polymer (45) with reactive B—Br groups, which is a poly-Lewis acid. ... 

The concept of using an excess of the alkyne to enhance vinylborane formation is not workable for an a,co-diyne if both alkyne moieties are to be hydrobo-rated. However, for example with 4 1 9-BBN l,8-nonadiyne stoichiometry, the l,l,9,9-tetra-9-BBN adduct is cleanly formed. The treatment of tetraborane adduct with 2 equiv of PhCHO results in the clean formation of trans,tram-, 9-di-9-BBN-l,8-nonadiene which on deuterolysis with AcOD affords the pure tranSytrans-didevLterated diene in 64% overall yield (Scheme 24.8) [27]. 

Scheme 7.2. Survey of cycles 2(n)-6(n) obtained from a,co-diynes 1(n) via Hay coupling, (a) Cu(OAc)2, pyridine/MeOH.

Well-defined Ru carbene catalysts, which are well known as very active catalysts for olefin metathesis reactions, have been elucidated to polymerize un- and substituted acetylenes such as a,co-diynes, propiolic acid esters, and DPAs. Grubbs 1st, 2nd-, and 3rd- (23-25, respectively. Figure 8) generation catalysts... 

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]. 

A limited number of examples of enantioselective [2 - - 2 - - 2] cycloaddition to give axially and central carbon chiral pyridine have been reported [23,30]. However, [2 -I- 2 -I- 2] cycloaddition to give a chiral pyridine by the kinetic resolution of racemic nitriles has not been reported (Scheme 5.17). The reaction of a, co-diyne 7 with racemic secondary nitrile in the presence of a catalytic amount of [Ir(cod)Cl]2/(/ )-Segphos gave chiral pyridine 47 in 75% yield with 80% ee. 

Use of the rhodium(I)-catalyzed double [2- -2-1-2] cycloaddition approach to the synthesis of symmetric biaryl diphosphorus compounds was first reported by Doherty et al. The reactions of l,4-bis(diphenylphosphinoyl)buta-l,3-diyne 81 with terminal a,co-diynes 80 proceeded at room temperature in the presence of the cationic rhodium(I)/BINAP catalyst to give symmetric biaryl bisphosphine oxides 82 in excellent yields (Scheme 9.29) [27]. Subsequent reduction of bisphosphine oxide 82 furnished the corresponding bisphosphine 83 (Scheme 9.29) [27]. 

Scheme 2.37 On-demand generation of an efficient catalyst for pyridine formation from unactivated nitriles 2.106 and a,co-diynes.

Kezuka, S., Tanaka, S., Ohe, T., Nakaya, Y. and Takeuchi, R. (2006) Iridium complex-catalyzed [2-1-2-1-2] cycloaddition of a,co-diynes with monoynes and monoenes. Journal of Organic Chemistry, 71(2), 543-552. 

A 50-60%-soln. of N,N-diethylprop-2-ynylamine in hexane passed al 65° during ca. 40 min. through a KNHa-on-alumina catalyst N,N-diethylprop-l-ynyl-amine. Y 65%. F. e. s. A. J. Hubert and H. G. Viehe, Soc. (G) 1968, 228 enamines from 2-ethyleneamines s. Soc. (G) 1968, 2048 1,3-dienes from acetylene derivatives, also conjugated tetraenes from a,co-diynes, s. Ghem. Ind. 1968, 975. 

The reaction of a.co-diynes with water afforded cyclized carbonyl derivatives in good yields (Scheme 22). The formation of cyclic carbonyl compotmd was... 

Carbocyclization of a,co-diynes was observed in Pd-catalyzed addition reaction (Scheme 8.36) [98]. Utilization of chelate phosphine ligand was of key importance to carry out this transformation only 5% of product was observed with PPh3, while 70% with dppe (100 °C, 1 h). 

Kanada J, Yamashita K, Nune SK, Tanaka M (2009) Pd-catalyzed addition-carbocyclization of a,co-diynes with H-P(0)R2 compounds. Tetrahedron Lett 50 6196-6199... 

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