Simple Stereoselective Synthesis of Eburnamonine

✍ Scribed by Friederike Klatte; Dipl.-Chem. Ulrich Rosentreter; Prof. Dr. Ekkehard Winterfeldt

• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 182 KB
• Volume: 16
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.197708781

✦ Synopsis

=c = C k 1 . (128) (a): R' = R2 = C sH5 ( b ) : R' = R2 = Fluorenylidene ( C ) : R' = H, R2 = CsH5 ever, such a pseudorotation is extremely difficult for steric reasons. Compounds ( I 2 A ) are therefore remarkably stable.

When heated dry to above its melting point (I 2a) undergoes 96% conversion into the allene (13a) (IR: VC=C=C 1933, vpz0 1198cm-'). After several hours' heating of (12b) in boiling toluene 76 % of the allene (13b) (IR: VC=C=C 1930, vp=o 1197cm-') and 8 % of fluorenone are isolated, the latter being formed by retro-cycloaddition.

Compounds having acidic CH2 groups [(lo), R' and RZ are groups exerting a -I effect] react with (7) via Michael addition and subsequent elimination of ethanol[71 to give the phosphaindoline ylides ( 1 4 ) , which are describable by several resonance structures.