Asymmetric Diels–Alder reactions of N-sulfinyl dienophiles using chiral Ti(IV) Lewis acids

✍ Scribed by Annette Bayer; Lars K. Hansen; Odd R. Gautun

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 407 KB
• Volume: 13
• Category: Article
• ISSN: 0957-4166
• DOI: 10.1016/s0957-4166(02)00661-4

✦ Synopsis

Enantioselective hetero Diels-Alder (HDA) reactions of 1,3-cyclohexadiene with benzyl N-sulfinylcarbamate 1a and with N-sulfinyl-p-toluensulfonamide 1b promoted by chiral Ti(IV)-based Lewis acids are reported. The obtained yields and enantiomeric excesses obtained are heavily dependant on the mode of catalyst preparation. Acceptable reproducibility was obtained with Ti(IV)-catalysts prepared from Me 2 TiCl 2 and chiral diols. Testing of various chiral diols gave the endo adduct in yields of up to 69% with 76% ee. The absolute configuration of the HDA products were established by chemical correlation and verified by X-ray crystallography.