Diastereoselective 1,2-Addition of Organometallic Reagents to Chiral Formylferrocenes Leading to Enantiomerically Pure Ferrocenyl Amino Alcohols: Application to Asymmetric Dialkylzinc Addition to Aldehydes and Synthesis of Optically Active 1,2-Homodisubstituted Ferrocenes

✍ Scribed by Shin-ichi Fukuzawa; Daisuke Tsuchiya; Kae Sasamoto; Kohki Hirano; Makoto Ohtaguchi

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 341 KB
• Volume: 2000
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/1099-0690(200008)2000:16<2877::aid-ejoc2877>3.0.co;2-u

✦ Synopsis

The chiral formylferrocenes 2-5 have been readily prepared in good yields by ortho-lithiation of the TMS-blocked orunblocked aminoferrocenes and subsequent reaction with DMF. The stereochemistry of the reaction of 2 with organometallic reagents has been examined. Reactions of 2 with Grignard and organolithium reagents gave the corresponding amino alcohol 6 in good yields with moderate to high diastereomeric excesses (up to 99%). When a dialkylzinc was used as the nucleophile, a single diastereomer was obtained almost exclusively. This reaction may be rationalized in terms of an autocatalytic mechanism; the zinc alkoxide 7 generated in situ functions as an activator of dialkylzinc, which then adds to the formyl group. We have examined the asymmetric diethylzinc addition to benzaldehyde using formylferrocenes 2-5 or ferrocenyl amino alcohols 6a, 13 as catalysts, especially with regard to the relationship between catalytic activ- [a