Stereocontrolled Synthesis of Angularly Fused Tricyclic Ring Systems by Means of 1-Metalla-1,3,5-hexatrienes (M=Cr, W)

✍ Scribed by He-Ping Wu; Rudolf Aumann; Roland Fröhlich; Birgit Wibbeling

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 295 KB
• Volume: 8
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/1521-3765(20020215)8:4<910::aid-chem910>3.0.co;2-t

✦ Synopsis

An efficient pathway for the stereocontrolled synthesis of functionalized, angularly fused tricyclic ring systems from readily available (1-alkynyl)carbene complexes [(OC) 5 M C(OEt)-CCR] (M Cr, W; R Ph, c-C 6 H 9 ) is described. The synthesis involves the formation of a 1-metalla-1,3,5-hexatriene from the (1-alkynyl)carbene tungsten complex [(OC) 5 WC(OEt)CCc-C 6 H 9 ] and a secondary amine, and its thermally induced p-cyclization to a tetrahydroindene, which undergoes a spontaneous isomerization to another tetrahydroindene. Condensation of these tetrahydroindenes with pyran-2ylidene complexes derived from (1-al-kynyl)carbene complexes [(OC) 5 MC-(OEt)CCPh] (M Cr, W) proceeds smoothly giving angularly fused tricyclic ring systems, rearrangement of which may generate spiro(cyclopentane-1,1-indanes) as side products. The synthesis is highly versatile and can be applied to the formation of various ring systems, such as steroid-type ring skeletons.