Benzo-fused heteroaromatic compounds, synthesis

Satoh, M. Miyaura, N. Suzuki, A. 1987. Palladium catalyzed cross-coupling reaction of (1-ethoxy-l-alken-2-yl)boranes with ortho-functionalized iodoarenes. A novel and convenient synthesis of benzo fused heteroaromatic compounds. Synthesis 373-377. 

Cyclodehydration of 2-hydroxy- or 2-aminobenzene-ethanal derivatives is known as a general procedure for the synthesis of benzo-fused heteroaromatic compounds [95]. Although numerous modifications of this general method have been explored, the major difficulty seems to be the lack of a general method for the synthesis of the required ortho-functionalized arene-ethanals. 

This reaction has the advantage that only one product (11) (head-to-head coupling product) is formed. Additional results are shown in Table 5. Aromatic bromides and iodides easily react with vinylic boron compounds, but organic chlorides do not participated, except the reactive allylic and benzylic derivatives. Heteroaromatic halides can be used as coupling partners. Or// o-substituents on benzene ring do not give difficulty. Thus, the cross-coupling reaction is used for the synthesis of benzo-fused heteroaromatic compounds (eq 5) (6). 

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