A New Approach to Inducing Silicon Tethered Ring-closing Metathesis Reactions

Ring-closing metathesis reactions involving diallyldiphenylsilane and diallyloxydiphenylsilane were successfully performed by using only 0 01 mol or even less of Grubbs' catalyst 1. The effects of reaction parameters, such as solvents, temperature and concentration of the catalyst are discussed.

Modular Total Synthesis of (-)-Palmyrolide A and (+)-(5S,7S)-Palmyrolide A via Ring-Closing Metathesis and Alkene Isomerization

A pentamodule assembly approach has been established for total synthesis of the naturally occurring(-)-palmyrolide A and(+)-5,7-epi-palmyrolide A.By using the racemic tert-butyl carbinol-containing alkyl iodide,the two diastereoisomeric macrolides could be obtained from the same sequence of reactions,demonstrating the flexibility of the multimodule assembly strategy for diverted total synthesis.

Halogen Bond Catalysis on Carbonyl-Olefin Ring-Closing Metathesis Reaction:Comparison with Lewis Acid Catalysis

The carbonyl-olefin ring-closing metathesis reactions have become a powerful tool for carbon-carbon bond formation.In this work,the halogen bond catalysis and classical Lewis acid catalysis on the carbonyl-olefin ring-closing metathesis reaction were investigated by density function theory.For both the halogen bond catalysis and classical Lewis acid catalysis,the carbonyl-olefin ring-closing me-tathesis reaction occurs by[2+2]-cycloaddition process and[2+2]-cycloreversion process,the reaction energy barriers are low,there-fore,it can be performed easily at room temperature.The essential difference of the two kinds of catalysts is that the catalytic mecha-nism of halogen bond catalysis is mainly contribution of electrostatic interaction,while that of classical Lewis acid catalysis is mainly catalyzed by orbital interaction.The halogen bond donor catalysts(ICI_(3),IF_(3))are expected to be efficient catalysts for the reaction and further promote the chemical synthesis of carbonyl-olefin ring-closing metathesis reaction.

新型麦角新碱中间体的合成

以2-甲基-3-硝基苯胺为起始原料,经Batcho-Leimgruber、酰化、还原、氧化、R)-叔丁基亚磺酰胺的不对称诱导、烯烃闭环复分解反应等关键步骤,共经12步反应合成了麦角新碱中间体(S)-4-溴-3-{[5-(甲氧基羰基)-1-甲基-1,2,3,6-四氢吡啶-2-基]甲基}-1H-吲哚-1-甲酸叔丁酯,总收率7. 2%,该路线涉及4个新化合物的合成,其结构经~1H NMR,^(13)C NMR和MS(ESI)表征。

Syntheses of Macrocyclic Amides from L-Amino Acid Esters by RCM

A series of succinate-derived macrocyclic amides（1） was synthesized via ring-closing metathesis（RCM） as the key step. The substrate included 12 to 15 members. The metathesis precursors were obtained from the amide coupling of ten-butyl 3-carboxyhex-5-enoate（2） with numerous side-chain aikenylated amino acid esters of general type（3） derived from L-lysine and L-ornithine.

Efficient Total Synthesis of （S）-Dihydroresorcylide, a Bioactive Twelve-Membered Macrolide

The efficient synthesis of （S）-dihydroresorcylide （la） along with trans-resorcylide dimethyl ether （2b）, was achieved in linear 9 steps from commercially available orcinol monohydrate （6） with esterification, carbonylation, and ring-closing metathesis （RCM） as the key steps in the synthetic sequence.