Transition heterocyclic cores

Despite its obvious limitation to the requisite preparation of copper(I) acetylides, this seminal work greatly influenced progress in the development of transition metal-catalyzed approaches for the preparation of benzofuran units, as well as other heterocyclic cores. Furthermore, since its original discovery, this protocol was featured in a number of syntheses of an array of multisubstituted benzofuran derivatives, including the preparation of various biologically active molecules and valuable intermediates [112-116]. 

Larger chiral heterocyclic core systems have been synthesized, for example chiral l,3-dioxanyl-4-ones (147) [114] methyldi-oxanyl (148) [116] and 2-alkyl-2,3-dihy-drobenzofuran (149) [117] derived meso-gens, and the phase behaviour and transition temperatures of these materials are shown below. 

Besides the applications of the electrophilicity index mentioned in the review article [40], following recent applications and developments have been observed, including relationship between basicity and nucleophilicity [64], 3D-quantitative structure activity analysis [65], Quantitative Structure-Toxicity Relationship (QSTR) [66], redox potential [67,68], Woodward-Hoffmann rules [69], Michael-type reactions [70], Sn2 reactions [71], multiphilic descriptions [72], etc. Molecular systems include silylenes [73], heterocyclohexanones [74], pyrido-di-indoles [65], bipyridine [75], aromatic and heterocyclic sulfonamides [76], substituted nitrenes and phosphi-nidenes [77], first-row transition metal ions [67], triruthenium ring core structures [78], benzhydryl derivatives [79], multivalent superatoms [80], nitrobenzodifuroxan [70], dialkylpyridinium ions [81], dioxins [82], arsenosugars and thioarsenicals [83], dynamic properties of clusters and nanostructures [84], porphyrin compounds [85-87], and so on. 

Most reactions discussed in this chapter rely on the formal attack of an electrophilic organometallic species on the electron-rich aromatic core of a five membered heterocycle. Depending on the way the transition metal... 

---