Total Synthesis of Dimethyl Glolosiphone Aviaα-Carbonyl Radical Spiro-Cyclization
摘要:
AbstractA general approach toward spiro[4.4]nonane structure based on the α‐carbonyl radical cyclization has been developed. Efficient total synthesis of dimethyl gloiosiphone A (2) was achieved. Thus, alkylation of the anion of dimethylhydrazone of cyclopentanone with 5‐iodopent‐1‐yne followed by hydrolysis gave ketone 4. Iodination of 4via its TMS‐enol ether yielded iodo ketone 7. Radical spiro‐cyclization of 7 gave spiro ketone 10. Iodination of 10 afford iodo spiro ketone 23. Oxidation and iodination of 23 gave compound 24. Methylation of 24 furnished methoxy iodo enone 25. Substitution of iodide in 25 with methoxide produced dimethoxy enone 26. Allylic oxidation of 26 gave diketone 27. Treatment of 27 with OsO4 and N‐methylmorpholine N‐oxide gave dihydroxy ketone 28. Methylation of the primary alcohol group in 28 afforded dimethyl gloiosiphone A (2).
In situ intramolecular catalytic 1,2-addition of allenoates to cyclic ketones towards polycyclic allenoates
作者:Clément F. Heinrich、Michel Miesch、Laurence Miesch
DOI:10.1039/c4ob02451f
日期:——
Sequential deprotonation, isomerization of 3-alkynoates and subsequent 1,2-addition led to bicyclic allenoate in the presence of a catalytic amount of Cs2CO3. Cyclization proceeds in a totally stereoselective manner in the case of the two-carbon linker chain. A one-pot reaction starting from alkynyl ketones afforded tricyclic fused ring systems with good yields.
在催化量的Cs 2 CO 3存在下,连续的去质子化,3-链烷酸酯的异构化以及随后的1,2-加成导致双环烯丙酸酯。在二碳连接子链的情况下,环化以完全立体选择性的方式进行。从炔基酮开始的一锅反应得到具有良好收率的三环稠合环系统。
Intramolecular reductive ketone–alkynoate coupling reaction promoted by (η2-propene)titanium
Intramolecular reductive coupling of cycloalkanones tethered to alkynoates in the presence of (η2-propene)titanium was successfully performed to provide hydroxy-esters in a diastereoselective manner. Subsequent lactonization afforded angularly fused unsaturated tricyclic lactones which represent relevant substructures of numerous bioactive compounds.
is presented. The procedure requires the easily available terminal alkynes as starting materials as well as commercially and readily available reagents such as diethylthiophosphite. The experimental procedure consists of a one‐pot process without any slow addition of one of the reagents.
Intramolecular radical cyclization of silylacetylenic or olefinic α-iodo ketones: Application to the total synthesis of (±)-modhephene
作者:Sha Chin-Kang、Jean Tsong-Shin、Wang Deh-Chi
DOI:10.1016/s0040-4039(00)97460-4
日期:——
Silylacetylenic or olefinic α-iodo ketones were treated with tributyltin hydride and AIBN to give bicyclic ketones by an intramolecular α-carbonyl radicalcyclization reaction. As an application of this radicalcyclization reaction, the total synthesis of (±)-modhephene has been accomplished efficiently.
that the oxidativeaddition of bis(pinacolato)diboron (1) to Pt(PPh3)4 generates cis-Pt(BO2C2Me4)2(PPh3)2 (5), whose structure was fully characterized by multinuclear NMR spectroscopies as well as single-crystal X-ray diffraction analysis. Complex 5 exhibited high reactivity for insertion to the alkyne giving 3 in high yields, thus implying that the oxidativeaddition of the B−B bond to a Pt(0) complex
四(甲氧基)-或双(频哪醇)二硼[[RO)2 BB(OR)2;(RO)2 =(MEO)2(图4a)和Me 4 c ^ 2 Ò 2(1)]添加到两个端子和内部炔烃中的Pt(PPH催化量的存在3)4,以提供sterEOdefined顺式-双(硼基)烯烃(3),收率极高。由于试剂和反应条件足够温和,因此该程序很容易扩展到各种官能化炔烃。机理研究表明,双(频哪醇)二硼的氧化加成(1)生成Pt(PPh 3)4生成顺式-Pt(BO 2 C 2 Me 4)2(PPh 3)2(5),其结构通过多核NMR光谱学和单晶X射线衍射分析得到充分表征。配合物5对插入炔烃显示出高反应活性,从而以高收率得到3,因此暗示将BB键氧化成Pt(0)配合物是铂(0)催化炔烃二硼化反应的第一步。 。