Sonogashira coupling reaction compounds

Spiro-linked compounds containing heterocyclic units have been prepared for many apphcations. In general, there are two synthetic pathways to build up heterocyclic spiro compounds. On the one hand, cross-coupling reactions like the Negishi, Kharash, Stille, Suzuki, or Sonogashira coupling reaction can be utilized to connect the heterocychc subunit with the central spiro core [118]. On the other hand, the heterocycle can be built up from spiro precursors containing heteroatoms. 

What starting materials could be used to synthesize each of the following compounds by PRACTICE PROBLEM G.8 a Sonogashira coupling reaction ... 

In this experiment, we will conduct some modern organic chemistry using a palladium catalyst. It is a rare opportunity for students in undergraduate laboratories to experience this powerful chemistry. We will react the lodosubstituted aromatic compounds, shown below, with 1-pentyne, 1-hexyne, or 1-heptyne in the presence of the catalysts, palladium acetate and cuprous iodide, to yield 4-substituted-l-pentynyl, 4-substituted-l-hexynyl, or 4-substituted-l-heptynylaromatic compounds. This reaction is called the Sonogashira coupling reaction. The reaction will be carried out in refluxing 95% ethanol as the solvent. In addition, piperazine will be employed both as a base and as a hydride donor. 

The direct crosscoupling of unfunctionalised aromatic compounds with terminal allgmes affords the same products as in the Sonogashira coupling reaction and is veiy attractive. 1,3,4-Oxadiazoles and oxazoles are coupled with terminal allgmes in the presence of a stoichiometric amount of cop-per(i) chloride at 120 °C under oigrgen (Scheme 15.56). Here, aUgmes must... 

Figure 5.17 General functionalization of brominated porphyrins to yield compounds suitable for Suzuki and Sonogashira coupling reactions.

The Sonogashira reaction is a C-C coupling reaction of terminal alkynes with aryl or vinyl halides in presence of Pd(0) metal and/or Cu(i) catalyst. These compounds are useful in synthesizing species having pharmaceutical... 

Like halopyridines, diazines participate in Sonogashira coupling too. 3,6-dimethyl-2-chloropyrazin, for example on coupling with phenylacetylene under standard conditions, gave the desired compound in good yield, which was further reduced to give a natural product (7.36.)51 (NB. the Heck reaction, which could be considered as an alternate approach would be expected to furnish predominantly the c/.v-olcfin as product). 

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