Triynes cyclic

Intramolecular 2 + 2 + 2-cycloisomerizations of cyclic triynes and enediynes have been reported with RhCl(CO)(PPh3)2.126 The transition metal-catalysed rearrangement of alk-5-ynals to /-alkynyl ketones and cyclopent-l-enyl ketones was developed using [Rh(P(OPh)3)2]BF4 or Cu(OTf)2 as a catalyst and the effect of substituents on the partition to products was elaborated (Scheme 84).127... 

Before leaving the diacetylenes we must note some of the stereochemical varieties available in their polymers. Triynes, 138, also polymerize in the crystal by 1,4-addition (213). Also, cyclic di- and polyenes give polymeric products on irradiation. The exact structure of the polymer, however, has been established only in the polymer 135. Note that alternate side chains in this polymer are on opposite sides of the plane of the main chain the polymer is thus meso. However, in principle such a reaction could give rise to optically active polymers in suitable structures. The cyclic tetradiyne 139 crystallizes in a polymerizable phase containing interstitial chloroform (209). The polymerization reaction, which involves... 

The isochroman 604 is capable of DNA cleavage and can be accessed via a poor yielding cycloaromatization of the 10-membered cyclic diyne 605 (Equation 247) <1996TL2433>. A rhodium- or mthenium-catalyzed [2+2+2] cyclization of the triyne 606 can be used to construct the tricyclic isochroman 607 in excellent yield (Equation 248) <2003JA7784, 2003JA12143>. 

The first phane hydrocarbon connecting two benzene rings by six bridges was claimed to be synthesized in 1973 by trimerization of the cyclic diyne 1743a. Yet the compound previously assigned the percyclophane-4 structure 18a later has been shown to be the triyne 18b43V) ... 

Toda and coworkers have found drastic differences in the reaction behavior of racemic and optically active 3,6-di-r-butylocta-l,4,7-triyne-3,6-diol (17) upon oxidative coupling by the Eglington method.- - Thus, the noncentrosymmetric cyclic dimers, (18a) and (18b), can be obtained from the racemic monomer, but the corresponding optically active monomer does not lead to any of the cyclic dimer. In the latter case the optically active polymer (19) is obtained as the sole isolable product (Scheme 7). 

Phosphorus tribromide [1. 873-874 874, after citation of ref. 5] 1-Bromocyclotri-deca-l,2-diene-4,8,10-triyne (2), a highly unsaturated 13-membered cyclic allene, was prepared in 20% yield by treatment of (1) with phosphorus tribromide in THF. The product (2) explodes at about 65° and slowly decomposes at 0° in the dark.53... 

Attempts to make a [3]pericyclyne by this strategy, starting from the symmetrical acyclic triyne 37 (from Fig. 9-10), failed in every case, which is not surprising, but they did not even give cyclic dimers, except for the disila[6]pericyclyne 84, which could be isolated in only 0.5 % yield (Fig. 9-24) [22]. It is not clear to us why 84 and the other [6]pericyclynes having two heteroatoms at opposite corners should be so difficult to form under these conditions. 

As well as cyclic compounds formally made up of alternate single and double bonds there are also cyclic hydrocarbons made up of alternating single and multiple bonds, the latter including both double and triple bonds. These compounds are known as dehydroannulenes for example cyclododeca-l,5,9-trien-3,7,10-triyne is called 1,5,9-trisde-hydro[12]annulene. 

Substituted tetraphenylenes are known as interesting biaryl-based chiral cyclic scaffolds. The cationic rhodium(l)/Cy-BINAP or QuinoxP complex-catalyzed enantioselective double homo-[2+2+2] cycloaddition of triynes afforded chiral tetraphenylenes with high enantioselec-tivity (Scheme 21.20) [24]. 

Intermolecular cyclization of diyne with monoynes or intermolecular cyclization of triynes is a general method for the synthesis of substituted benzenes [51]. But a serious drawback of this reaction is the presence of a secondary process of diyne dimerization or monoyne trimerization. The selectivity and yield of the cyclic products strongly depend on the structure of the reactants, solvent, catalyst, etc. A highly efficient and selective [2-I-2-I-2] cyclization of diynes and monoynes was described. A rhodium catalyst allowed the reaction to proceed at room... 

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