Reactions of cyclic alkynes with metal compounds

5 Reactions of Cyclic Alkynes with Metal Compounds 

This section is short, for two main reasons (1) there are two other chapters in this book (Chapters 4 and 5) devoted to the metalorganic chemistry of acetylenes, and (2) there are several recent reviews dealing with metal compounds [lb, c, 72-77]. Therefore we will deal here only with very recent reactions which are typical for cyclic mono- and diynes. 

The reaction of cyclic diynes with CpCo(CO 2 or CpRh(CO)2, or in some cases with Fe(CO)5, leads to the tricyclic cyclobutadiene complexes, as demonstrated for the reaction of 1,7-cyclododecadiyne (3) with CpM(CO)2 in Eq. (24). This reaction was discovered and explored 20 years ago [77, 79]. The availability of cyclic diynes with uneven chains such as 1,6-cyclodecadiyne (100), 1,8-cyclotetradecadiyne (120) and 1,10-cyclooctadecadiyne (168) led to the superphanes 169-171 and to the intramolecular complexes 172-174 [Eq. (25)] [1 c, 80]. 

While the one-pot reaction is limited so far only to diynes with uneven chains and to CpCoL2 complexes, a route has been designed which allows the synthetic of superphanes 

It is interesting to note that the reaction of the sulfur-containing diynes shown in Eq. (26) with CpCo(CO)2 leads not to the anticipated cyclobutadiene complexes but to the thiopheno-phanes [83]. This reaction works even with catalytic amounts of the CpCo complex. 

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