The Sonogashira-Hagihara Reaction

In 1975, Sonogashira and coworkers [23] reported a novel Pd(0) cross-coupling (more appropriately known as the Sonogashira-Hagihara reaction) reaction of terminal alkynes with vinyl and aryl... 

Table 1.2 The ligands and the TON values reported and obtained in the Sonogashira-Hagihara reaction reported by Evonik Degussa [111].

In contrast to the variety of synthetic procedures, which proved to be important for the preparation of OP Vs, the Sonogashira-Hagihara reaction represents by far the dominating process for the generation of OPEs. The mechanism of the Pd-catalyzed CC coupling between an iodoarene R -I and an ethynylarene R -C=CH is outlined in Scheme 11.15. 

Scheme 11.15. Catalytic circle of the Sonogashira-Hagihara reaction (Instead of iodoarenes R I, bromo compounds or electrophiles with other leaving groups can be used Cul as cocatalyst can be omitted when iodobenzene derivatives are used.)...

The Suzuki coupling reaction of tetrabromopyrene 59 with appropriate boronic acid ester yields tetraaryl-pyrenes 69, see Scheme 4.18 [112, 113] while the Sonogashira-Hagihara reaction in between 59 and 3,4,5-tridodecyloxyphenylacetylene produces 1,3,6,8-tetrakis(3,4,5-fiisdodecyloxypheny-lethynyl)pyrenes 70 [114]. 

Cross-coupling of terminal acetylenes used as nucleophiles with aryl or alkenyl halides (referred to as the Sonogashira-Hagihara, or SH, reaction) is a versatile method of synthesis for acetylenic compounds, which are rapidly gaining importance as advanced new materials and building blocks for implementing unusual molecular architectures. 

Beletskaya, I. P., Latyshev, G. V., Tsvetkov, A. V., Lukashev, N. V. The nickel-catalyzed Sonogashira-Hagihara reaction. Tetrahedron Lett. 2003,44, 5011-5013. 

Furthermore, a number step growth metal-catalyzed C—C combining reactions like Stille, Kumada, or Suzuki coupling, Heck and Sonogashira-Hagihara reactions, a.o., are employed especially for the preparation of highly aromatic and conjugated polymers (see Fig. 3.21). 

The first synthesis of PPEs was published by Schulz and Giesa in 1990 [3]. They reacted dibromodi(alkoxy)benzenes with different di(ethynyl)di(alkoxy)arenes in the presence of a Pd catalyst in an amine (Heck-Cassar-Sonogashira-Hagihara reaction) [4]. They obtained low molecular weight... 

Alkynylsilane Cross-Couplings-The Sila-Sonogashira-Hagihara Reaction... 

Scheme 9.44 Fluoride and Cu(l) activation of alkynyltrimethylsilanes 120 in the sila-Sonogashira-Hagihara reaction [319, 320].

Significantly higher yields were, however, achieved in the absence of a Pd catalyst for this procedure and hence sparked interest in Pd-free variants of the sila-Sonogashira-Hagihara reaction. A simple, but efficient system used the inexpensive and readily available CuCl/PPhj combination for the catalytic cross-coupling of alkynylsilanes with aryl iodides [322]. 

An interesting variant of the sila-Sonogashira-Hagihara reaction avoiding any transition metal catalysts has more recently been reported by Portella et al [332]. The catalytic cycle was implemented under fluoride activation while replacing... 

Scheme 1.8 (a) General conditions for the Songashira-Hagihara cross-coupling reaction, (b) The proposed mechanism for the Sonogashira-Hagihara cross-coupling arylation procedure [12, 24]. 

Figure 1.31 The palladacycle catalysts used by Dupont s group [109] for copper-free Sonogashira-Hagihara reaction arylations.

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