Hypervalent boron heterocycles

More recendy, Akiba and coworkers have synthesized pentacoordinated hypervalent boron heterocyclic species 4—6 by employing a sterically rigid anthracene skeleton (Scheme 1) (2000ACE4055,2005JA4354). Compounds 6—8 were prepared by lithiation of bromoanthracene 4 followed by the addition of E-chlorocatecholateborane derivatives 5. Products 6—8 were... 

Keywords Benziodoxoles Hypervalency Hypervalent Hypervalent boron Hypervalent bromine Hypervalent heterocycles Hypervalent iodine Hypervalent silicon Hypervalent sulfur Iodine heterocycles... 

A similarly coordinated 10-methylacridinium-based hypervalent boron-oxygen heterocyclic system 10 has been synthesized by Yamamoto and coworkers starting from compound 9 as outlined in Scheme 2 (2009 CL794). The hypervalent nature of the O—B—O has been confirmed by X-ray structural data (the average B—O bond of 2.51 A). 

Another example of a hypervalent boron—oxygen heterocyclic stmcture is represented by the 2,6-bis(p-tolyloxymethyl)benzene-based 10—B—5... 

Vidovic, Findlater, and coworken reported the synthesis and characterization of terpyridine-based hypervalent 10—B—5 boron—nitrogen dica-tionic heterocycle 16 (Scheme 4) (2013IC13865). The X-ray molecular structure of derivative 16 revealed evidence for pentacoordination at boron with four shorter B—N bonds (between 1.50 and 1.63 A) and one longer bond of 2.94 A. 

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