Tolanes, preparation

Probably the most interesting materials to exhibit TGB phenomena are the tolanes prepared by Nguyen and coworkers [45-47]. In their exhaustive and beautiful studies of materials that exhibit TGB phases, Nguyen et al. have prepared many series of tolanes that are substituted at one end with a 4-n-alkoxybenzoyloxy group and at the other terminus with an ester or ether moiety that carries a chiral functionality, see Figs. 36 and 37. Their early work... 

Other siloles cannot be prepared directly from the alkyne and lithium as tolane is the only one to give the diene dianion. However, oxidative dehydrogenation of the silacyclopen-tane (Scheme 192) (67JOC885, 73MI12000) gives a route to 2,5-substituted siloles, e.g. (120),... 

The preparation of the related high molecular weight poly-1.4-phenylene sulfide has been accomplished by heating />-bromothio-phenolate salts in pyridine at 250° C (57). The commercially available polyethersulfones are reported to be prepared by condensation of 4.4 -dichlorodiphenyl sulfone with salts of biphenols in solvents such as dimethylsulfoxide at 150° C. The work of Bacon and Hill would suggest that both of these reactions might be carried out at considerably lower temperatures with copper (I) salts as catalysts. In addition, it has been demonstrated that copper (I) acetylides react quantitatively with aromatic iodides to yield tolanes (15, 77) therefore this reaction should also be the basis for a similar polymer forming reaction. 

Dihydrogermoles 250 are prepared by ring rearrangement and insertion starting from the bicyclic compound 249, when it is heated with tolane in benzene <20010M3364>. 

The reaction of aryl halides 1 with alkynylcopper(I) 2 under reflux in pyridine to prepare internal arylacetylenes is known as the Stephens-Castro reaction [Eq. (1)] [2]. The reaction has proved to be particularly important in the synthesis of a wide range of tolan and heteroaromatic alkynes [3]. Vinyl and allenic halides can also be used and several reviews... 

Alkyne cyclotrimerization occurs at various homogeneous and heterogeneous transition metal and Ziegler-type catalysts [7], Substituted benzenes have been prepared in the presence of iron, cobalt, and nickel carbonyls [8] as well as trialkyl- and triarylchromium compounds [9]. Bis(acrylonitrile)nickel [10] and bis(benzonitrile)palladium chloride [11] catalyze the cyclotrimerization of tolane to hexaphenylbenzene. NiCl2 reduced by NaBH4 has been utilized for the trimer-ization of 3-hexyne to hexaethylbenzene [12]. Ta2Cl6(tetrahydrothiophene)3 and Nb2Cl6(tetrahydrothiophene)3 as well as 7 -Ind-, and 77 -Ru-rhodium... 

Castro, C. E., Stephens, R. D. Substitutions by iigands of iow vaient transition metals. A preparation of tolans and heterocyclics from aryl iodides and cuprous acetyiides. J. Org. Chem. 1963, 28, 2163. 

Cyclic acetylide titanium complexes containing the 0-bis(ethynyl)tolane ligand have been synthesized, characterized, and used to prepare a heterobimetallic derivative with an Ni atom coordinated to three alkyne functionalities (Scheme 501).1286... 

Bcnzynes.s LiTMP is also an effective base for formation of benzynes from ArCl. Thus treatment of o-chloroanisole with LiTMP and LiC=CC6H5 gave m-rneth-oxytolane (1, tolane = diphenylacetylene) in 80% yield. Diphenyl sulfide was prepared in 93 % yield from C6H5C1, C6H5SLi, and LiTMP. 

The preparation of certain A1 heterocycles [e.g., triphenylbenzaluminole by heating the addition product from triphenylalane and tolane (64) (see Section V,C,2)] can only be mentioned here. 

New reactions of isoquinoline derivatives include the following 3,4-di-hydroisoquinoline N-oxide with 2-acetylcycloalkane-l,3-diones, Reissert compounds with stilbene and tolan derivatives, isoquinoline with pyrrole derivatives and with 2-methylfuran " (both in the presence of benzyl chloride), and the chromium trioxide oxidation of the benzo[a]quinolizidine (49) to give (50). Compound (49) was prepared by the condensation of 3,4-dihydroiso-quinoline with the 5-lactone (51). Further examples of a classical benzo[a]-... 

Various Carbocyclic Fused Systems.—l,3-diphenyl-4//-5,6-dihydrocyclo-penta[c]thiophen-c/5-4,6-dicarboxylic acid has been prepared by the reaction of the appropriate 1,4-diketo-derivative with phosphorus pentasulphide. The reaction of (169) with tolane gave (170). Acylation of 2-methoxy-... 

Similar tolane systems to those reported by Nguyen have been prepared by Walba et al. [53] for the purposes of studying NLO effects in liquid crystals, and in particular in ferroelectric phases. The two families of materials, which have lateral nitro-substituents, are shown in the general structures 9 and 10. Most of the ethers, 9, are reported to exhibit phases, which have relatively large... 

PMMA samples with dopant molecules were prepared by polymerizing MMA doped with either stilbene or tolan. The composition of the initiator and chain-transfer agent and the condition of polymerization were almost the same as the above copolymerization. 

Scheme 4.5 shows the most important direct routes for preparing soluble PAVs Heck coupling, and Wittig and Horner polycondensations. The two biggest advantages of these routes are that they avoid the formation of tolane and other defects seen in the precursor routes, and also that they allow the synthesis... 

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