6.7- Dimethoxy-2-tetralone

Schmidt rearrangement of an azido ketone. Thus, 6,7-dimethoxy-2-tetralone (219) has been reacted with methyl ( )-7-iodo-2-heptenoate (220) affording stereoselectively the Cl-spiroketone 221 in 48% yield. After transformation of the latter to the azido derivative 222 the tetracyclic lactam 223 was obtained under ring expansion possessing the schelhammeridine core. Finally, LiAlH4 reduction smoothly provides the ( )-3-demethoxy-l,2-dihydrocomosidine base 224 (772) (Scheme 41). 

Hydrogenolysis of aromatic carbonyls occurs mainly by conversion to the benzyl alcohol and its subsequent loss. If hydrogenolysis is desired, the usual catalyst is palladium 38). Hydrogenolysis is facilitated by polar solvent and by acid (55). For instance, hydrogenation of 3,3-dicarbethoxy-5,8-dimethoxy-l-tetralone (5) over 5% Pd-on-C gave 6 quantitatively 54) when hydrogen absorption ceased spontaneously. 

Dihydroxy-l-tetralone Diisoprene 2,3-Dimethoxy-5,6-dimethyl-l,4-benzoquinone Isosclerone ( )-Limonene Aurantiogliocladin... 

Condensation of 2,2-dimethoxy-l-methyl pyrrolidine(piperidine) with 1-indanone, 1-tetralone, 4-thiochromanone, butyrolactone, phthalide and substituted 2-oxindoles gives the corresponding enaminoketones614. 

The enamide 73 was prepared from 2,3-dimethoxy-5,6-methylenedioxy-benzoic acid and 6,7-methylenedioxy-l-tetralone, and was then irradiated to afford the lactam 74 in 38% yield. On acid treatment 74 was converted to the dehydrolactam 75 as a result of the elimination of the migrated meth-oxyl group. Dehydrogenation with 30% Pd/C, reduction with vitride, followed by treatment with DDQ, completed total synthesis of chelirubine (76) 91,92) (Scheme 43). 

K pulverized in xylene, which is then replaced by benzene, 5,8-di-methoxy-2-tetralone added in a N2-stream under anhydrous conditions, gently refluxed for 40 min., methyl iodide added, heated 30 min., and allowed to stand overnight —> l-methyl-5,8-dimethoxy-l,2,3,4-tetra-hydronaphthalene. Y 90%.—The insoluble K-salt of the starting material prevents double methylation. (C. A. Grob and W. Jundt, Helv. 31,1691 (1948).)... 

Aza-annulation of a number of dimethoxy-substituted P-tetralone derivatives, such as those represented by 136, with acrylamide was used to produce 137. In turn, 137 was an important intermediate in the synthesis of conformationally restricted congeners of dopamine (eq. 30).53... 

---