Asymmetric synthesis of 2,4-disubstituted butyrolactones using the iron chiral auxiliary [(η5-C5H5)Fe(CO)(PPh3)]

✍ Scribed by Stephen G. Davies; Robert Polywka; Peter Wamer

• Publisher: Elsevier Science
• Year: 1990
• Tongue: French
• Weight: 627 KB
• Volume: 46
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)85598-8

✦ Synopsis

Treatment of the lithium enolate derived from homochiral S-](qS-CSHS)Fe(CO)(PPh3)COCH2CH3] with homochiral R-or S-propylene oxide or R-styrene oxide in the presence of diethylaluminium chloride followed by oxidative decomplexation generated cis-2S,4R-dimethyl butyrolactone, trans-2S,4S-dimethyl butyrolactone and cis-2S,4S-2-methyl-4phenyl butyrolactone respectively. An X-ray crystal structure of the latter compound established unambiguously the relative and absolute configurations. Treatment of the lithium enolate from homochiral R-[(q5-CSHS)Fe(CO)(PPh3)COCH2CH3]

with R-styrene oxide in the presence of diethylaluminium chloride followed by oxidative decomplexation generated trans-2R,4S-2-methyl-4phenyl butyrolactone.

In the presence of diethylaluminium chloride the enolate from S-[(qs-CSHS)Fe(CO)(PPh3)COCH2CH3] with racemic styrene oxide exhibited chiral discrimination in favour of the R-epoxide to the extent of >loO:l.