Synthesis of porphyryl boronates with (un)saturated side-chains

Porphyrins with (un)saturated side-chains containing boron residues were developed as synthons for porphyrin functionalisation. Porphyrins with mono and bis-substituted unsaturated boronyl residues were prepared in good yields (52-66%) using a cross-metathesis approach in the presence of Grubbs I-generation catalysts. In all cases complete E-stereoselectivity (100%) was observed. Furthermore, formal cross-metathesis products with alpha,beta-unsaturated chains smoothly underwent addition with bis(pinacolato) diboron [(Me(4)C(2)O(2))B-B(O(2)C(2)Me(4))] to yield the corresponding saturated boron compounds in 60-70% yields. (C) 2008 Elsevier B.V. All rights reserved.