Origins of π-face selectivity in the aldol reactions of chiral E-enol borinates: a computational study using transition state modelling.

✍ Scribed by Anna Vulpetti; Anna Bernardi; Cesare Gennari; Jonathan M. Goodman; Ian Paterson

• Publisher: Elsevier Science
• Year: 1993
• Tongue: French
• Weight: 758 KB
• Volume: 49
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)86270-0

✦ Synopsis

A molecular mechamcs translhon state model 1s used to analyse the stereoselechvlty of a sene~ of aldol reacbons of E-en01 bormates of type 3 wth aldehydes The model reproduces the sense and degree of x-face selectlvlty for the choral E-enol bormates 8,11,13 and 14 m the Table Enolates 8 and 10 preferenhally attack the re-face of aldehydes, which IS explamed (Scheme 5) by the aldol addlhon proceedmg through the preferred transltlon structure TS-A for both electromc and stenc reasons In contrast, enolates 11,13 and 14 preferentially attack the sr-face of aldehydes solely for stenc reasons, which IS explamed by mvokmg the favoured translhon structure TS-B denved from the modelhng results These two translhon state models, TS-A and TS-B, which apply to E-enol bormates, differ substantially from the translhon state model, TS-C, used for choral Z-enol bormates with slmllar subshtuents Our force field model of the boron aldol translhon state IS shown to be useful m understandmg the ongms of the Xface selechvlty over a wde range of substrates