Diacetylenes, cyclic

Acetylene- and Diacetylene-Expanded Cycloalkanes and Rotanes. 201 1 - 42 Diederich F, Gobbi L (1999) Cyclic and Linear Acetylenic Molecular Scaffolding. 20J 43 - 79 Gobbi L, see Diederich F (1999) 201 43 -129... 

Only two general methods have been developed for the synthesis of the macrocyclic annulenes.9 The first of these, developed by Sondheimer and co-workers, involves the oxidative coupling of a suitable terminal diacetylene to a macrocyclic polyacetylene of required ring size, using typically cupric acetate in pyridine. The cyclic compound is then transformed to a dehydroannulene, usually by prototropic rearrangement effected by potassium i-butoxide. Finally, partial catalytic hydrogenation of the triple bonds to double bonds leads to the annulene. 

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... 

Using this method, several mesogen diacetylenes were obtained [49]. Palladium-catalysed coupling of an allylic cyclic carbonate with 1-pentynyl phenyliodonium tetrafluoroborate to give an enyne was highly successful [50]. Alkynyl iodonium triflates and lithium salts of diethyl 2-[(diphenylmethylene)amino]malonate were used for the preparation of alkynyl-a-amino acid derivatives, e.g. [51] ... 

The absorption spectra of the charge transfer complexes of 1,3-diacetyIenes were recently measured. Table 1 shows maxima of one-to-one tetracyanoethylene (TCNE) complexes of dialkyl-1,3-diacetylene and related compounds. The cyclic tetrayne (8b)-TCNE complex shows a normal absorption spectrum regardless of the closed, parallel conformation of the two diacetylene groups in 8b. This is in striking contrast... 

The jp-carbons of 4a are deshielded by 14-5 p.p.m. from the chemical shift (8T3 p.p.m.) of those of cyclotridecyne. This remarkable effect has been ascribed to partial olefinic character of the triple bonds caused by large molecular deformation . In fact the c/.y-oIefinic configuration has recently been confirmed by X-ray structure analysis of 25 As to the chemical shifts of acetylenic jp-carbons in cyclic tetraacetylenes, both of the inner and outer sp-carbons of 8b are deshielded by ca. 3 p.p.m. relative to the corresponding carbons of acyclic diacetylenes (Figure 5). 

The photoelectron spectra of cyclic diacetylenes, 4a and 6a and a reference compound, cyclooctyne were measured in order to study the proximity interaction of acetylenic bonds . The observed values of the lowest vertical ionization potentials were in the order 6a > 4a > cyclooctyne. The photoelectron bands were assigned by scmiempirical calculations, MINDO/2 and SPINDO, using X-ray crystallographical data, and their relative sequence and positions were explained in terms of through-bond and through-space interactions between 7t and a orbitals. 

The cyclic diacetylene 5,6,1 l,12-tetradehydrotetrabenzo[a,c,g,i]cyclododecahexa-ene 89 is particularly interesting for its two triple bonds are closely fixed and cross each other, and the four j-p-carbons occupy the apices of an expected tetrahedrane (90). In view of this, 89 was synthesized from bis(2-bromophenyl)acetylene (88) by... 

An attractive transformation of cyclic diacetylenes (4) to cyclobutadienes (92) was attempted considering the proximity interaction, but it has been unsuccessful so far. However, transition metal complexes such as the u-cyclopenladienyl cobalt... 

Besides processes (1) and (2), the reader should be aware that nucleophilic attacks on alkynes are treated in other chapters of this book, dealing with rearrangements, cyclizations, polyacetylenes, cyclic acetylenes and perhaps others. A number of publications overlap with ours in different ways and at different levels -. They treat individual alkynes or families " , e.g. acetylene, diacetylenes , acetylene dicarboxylic esters haloacetylenes , alkynyl ethers and thioethers > ynamines , fluoro-alkynes ethynyl ketpnes , nitroalkynes , etc. synthetic targets, e.g. pyrazoles , if-l,2,3-triazoles , isothiazoles , indolizines S etc. reagents, e.g. nitrones , lithium aluminium hydride , heterocyclic A -oxides - , azomethine ylids - , tertiary phosphorus compounds , miscellaneous dipolar nucleophiles - , etc. The reader will appreciate that all of these constitute alternate entries into our subject. 

The solid-state polymerization of the following classes of monomers is discussed diacetylenes, monoacetylenes, mono- and dienes, ring-opening cyclic monomers, and transition metal systems. With particular emphasis on open questions and current problems, the chemiced, structural, and physical properties of the resultant polymers are sununarized. A brief prognosis is offered. 

The outline of this article is as follows. After general remarks tUsout the solid-state polymerization process, adopting the view that it is important to develop new types of solid-state polymerization, the polymerization of the following classes of monomers will be discussed diacetylenes, monoacetylenes, vinyl and diene monomers, cyclic systems which ring open, and transition metal systems. It is implicit in the discussion that appropriately substituted forms of the above monomers may be polymerized as mono-layers and multilayers (11-13) as well as in the form of inclusion complexes (14). Emphasis will be placed on topics of current interest. 

Ionization potential of Continued) butenone, 123 cyclic diacetylenes, 305 cyclohexene, 48, 102 cis-cyclooctene, 102 Zraus -cyclooctene, 102 DABCO, 81 dimethyl ether, 123 ethylene, 80, 319 formaldehyde, 123, 319 hydrogen atom, 55, 75 methanol, 123 methyl acetate, 123 methyl acrylate, 123 nitrous oxide (N2O), 172 norbornadiene, 48 norbornene, 48 oxetane, 123 tetrahydrofuran, 123 trimethylamine, 81 water, 123... 

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