Diyne reaction

The preparation of condensed rhodacyclopentadienes via the diyne reaction, and examples of their use in heterocyclic synthesis have been described earlier (see Schemes 79 and 86 in Sections IV,B,5 and IV,C,2). An example showing the application of this approach to the synthesis of a condensed triazole is shown in Scheme 127.192... 

The diyne reaction has been used extensively by Muller et al. in heterocyclic synthesis (see for example Scheme 86 in Section IV,C,2) a process using a diyne substrate and leading to the formation of an azuleno[l,2-d]-dibenzo[b,/]silepin is shown in Scheme 172.243fl... 

Cyclic addition reactions of 16a with diynes or cyanamide are interpreted as being initiated by an electrophilic attack of the cyanamide or the terminal carbon atom of a C=C bond. Both result in ring expansion and the formation of 2,4-As,As-diphosphapyridine 39 <1998ZNB443> or l,3-A5,A5-diphosphabenzenes 40, respectively (Scheme 10). The diyne reaction is not limited to conjugated systems. 1,5-Hexadiyne and 1,7-octadiyne can be used as well <1997JOM(529)223>. 

The ene-diyne reaction (Bergman cyclization) chemistry described below is not part of the biologically related radical reactions. However, after the successive discovery of... 

Buta-l,3-diyne, reaction with ethylenediamine, 56, 9 Butane-2,3-dione, perlluoro-, heterocycles from, 59, 17... 

The diyne reactions of 1,4-, 1,5-, 1,6-, and 1,7-diynes via transition metal complexes are useful for the synthesis of new cyclic compounds (Muller, 1974 Wagner and Meier, 1974, 1975). t-C5H5Co(CO)2 reacts catalytically with linear l,m-diacetylenes (XXXVIII) to give trimers (XXXIX), formation of which involves the interaction of six acetylene functions (Vollhardt and Bergman, 1974). 

Mixed cyclizations also have been achieved via the diyne reaction [Eq. (82)]. Most of the diynes employed thus far have been symmetrical, leading, therefore, to symmetrical rhodacycles. A few representative examples are provided below. An interesting variation is the addition of strained... 

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