在此,我们报告Cp * Co III催化的C H活化方法是创建高度有价值的异喹诺酮和吡啶酮的重要步骤,这些异喹啉酮和吡啶酮可以轻松地用于各种芳香族素,原小ber碱和tylophora生物碱的总合成。这种特殊的CH活化/环化反应是通过多个末端以及内部炔烃偶联伙伴实现的,具有广泛的应用范围和出色的官能团耐受性。本文报道的该方案的合成适用性已在两个Topo-I-抑制剂和两个8-氧代小ber碱核心的合成中得到了证明,这些核心可进一步制成四氢小ber碱和原小ber碱生物碱。此外,这些构件也以方便的方式转化为六种不同的tylophora生物碱。
Rhodium(III)-Catalyzed Intramolecular Annulation through CH Activation: Total Synthesis of (±)-Antofine, (±)-Septicine, (±)-Tylophorine, and Rosettacin
作者:Xianxiu Xu、Yu Liu、Cheol-Min Park
DOI:10.1002/anie.201204970
日期:2012.9.10
Annulation: The efficient synthesis of 3‐hydroxyalkyl isoquinolones and 6‐hydroxyalkyl 2‐pyridones is enabled through the intramolecular annulation of alkyne‐tethered hydroxamic esters (see scheme, Cp*=pentamethylcyclopentadienyl). The reaction features high regioselectivity, broad substrate scope, and excellent functional‐group tolerance, proceeds under mild reaction conditions with low catalyst loading
An Isomünchnone-Based Method for the Synthesis of Highly Substituted 2(1<i>H</i>)-Pyridones
作者:Albert Padwa、Scott M. Sheehan、Christopher S. Straub
DOI:10.1021/jo9911600
日期:1999.11.1
1-(Benzenesulfonyl-diazoacetyl)-pyrrolidin-2-one was prepared by a diazo transfer of 1-(benzenesulfonylacetyl)-pyrrolidin-2-one with p-acetamidobenzenesulfonyl azide and triethylamine. Treatment; of the diazoimide with a catalytic quantity of rhodium(II) acetate resulted in the formation of an isomunchnone dipole, which underwent bimolecular trapping with various dipolarophiles in high yield. The initially formed cycloadducts were not isolable or observed, as they all readily underwent ring opening to give the 3-hydroxy-2(1H)-pyridone ring system. The 3-hydroxy-2(1H)-pyridones were readily converted to the corresponding triflates, which function as suitable substrates in various types of palladium-catalyzed cross-coupling reactions. Commercial tetrakis(triphenylphoshine)palladium was found to be a particularly effective catalyst for the cross-coupling with aryl, vinyl, and acetylenic partners. An application of the method to the synthesis of the indolizidine alkaloid (+/-)-ipalbidine was carried out in eight steps in 17% overall yield. The angiotensin-converting enzyme inhibitor (-)-A58365A was also synthesized by a process based on the [3 + 2]-cycloaddition reaction of a phenylsulfonyl substituted isomunchnone intermediate. The starting material for this process was prepared from L-pyroglutamic acid and involved using a diazo phenylsulfonyl substituted pyrrolidine imide. Treatment of the diazoimide with Rh-2(OAc)(4) in the presence of methyl vinyl ketone afforded a 3-hydroxy-2-pyridone derivative, which was subsequently converted to the ACE inhibitor in six additional steps.
Synthesis of (±)-septicine
作者:Benjamin R. Yerxa、Kevin Yang、Harold W. Moore
DOI:10.1016/s0040-4020(01)80639-6
日期:1994.1
The total synthesis of the indolizidine alkaloid, (+/-)-septicine (5) (27% overall yield) in 8 steps from dimethyl squarate is presented. The key step of the synthesis involves the ring expansion of 2,3-bis-(3,4-dimethoxyphenyl)-4-(1-pyrrolo)cyclobutenone 12 to the corresponding indolizine-5,8-dione 6. The synthesis is highly convergent and thus could be used for the synthesis of a variety of analogs.