Enantioselective synthesis of rigid 2-aminotetralins. Utility of silicon as an oxygen and nitrogen surrogate in the tandem addition reaction.
Dimethylphenylsilyllithium undergoes a highly diastereoselective conjugate addition to chiral naphthyloxazoline 11. Electrophilic trapping of the resulting aza-enolate affords the tandem addition product (12) in high yields as a single diastereomer. The silicon, thus incorporated, may be protodesilylated and undergoes a Tamao oxidation to afford the corresponding alcohol. By chemical modification of the oxazoline, both the gamma-lactone (28) and the delta-lactone (37) were prepared. Reduction of each lactone followed by oxidation of the ensuing diol gave the keto aldehyde. Double reductive amination of the 1,4-dicarbonyl (from the gamma-lactone) allowed the synthesis of two novel hexahydrobenz[e]indoles, 20 and 35. Double reductive amination of the 1,5-dicarbonyl (from the delta-lactone) gave access to two novel octahydrobenzo[f]quinolines, 41 and 43. An unprecedented rearrangement of nitro alcohol 26 into lactone 28 is described and a reasonable mechanism for its formation postulated.
Degnan
A P
AP
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
Meyers
A I
AI
D000978:Antiparkinson Agents / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy; D009584:Nitrogen / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D013237:Stereoisomerism; D013764:Tetrahydronaphthalenes / Q000138:chemical synthesis*
D000978:Antiparkinson Agents; D013764:Tetrahydronaphthalenes; D009584:Nitrogen; D010100:Oxygen; D012825:Silicon