For example, chiral dirhodium complexes catalyze the intramolecular C-H insertion of α -diazo -β -ketoester to give the intermediate for the total synthesis of the marine secosteroid (-)-astrogorgiadiol (Scheme 3). Up to 58% de is observed with moderate yield of 38% employing Rh2( S -biTISP)2 as the catalyst. The reaction using Rh2 (S-PTPA)2 afforded excellent yield but with lower diastereoselectivity.
Scheme 3. Synthetic Studies toward (-)-Astrogorgiadiol
ortho -Metallated arylphosphine dirhodium(II) complexes are found to be effective catalysts for intramolecular C-H insertions of certain diazoketones (Scheme 4). One of the examples is the use of dirhodium complex 1 for the reaction of chloro-substituted system to afford cyclophentanone in 74% ee and 87% yield. This system works well with the aryl portion having electron withdrawing group.
Scheme 4