Asymmetric Synthesis of the Tricyclic Core of <i>Calyciphylline</i> A-Type Alkaloids via Intramolecular [3 + 2] Cycloaddition
作者:Lu Wang、Chen Xu、Li Chen、Xiaojiang Hao、David Zhigang Wang
DOI:10.1021/ol403609c
日期:2014.2.21
Asymmetric synthesis of the [5–6–7] tricyclic system common to the Calyciphylline A-type alkaloids is reported, featuring Overman rearrangement, Heckcyclization, intramolecular [3 + 2] cycloaddition, diastereoselective hydrogenation, and Claisen rearrangement as strategic events. The approach is capable of installing the crucial carbonyl functionality as well as multiple stereogenic centers within
modification of non-ordered mesoporous silica supports, starting from niobocene dichloride via solvent-less organometallic precursor dry impregnation or conventional liquid-phase grafting technique. Grafted Nb/SiO2 solids were used as catalysts, in the presence of aqueous H2O2, for the epoxidation of unsaturated cyclic and terpenic compounds of interest for fine and specialty chemistry, in particular:
从二氯化铌通过无溶剂有机金属前驱体干法浸渍或常规液相接枝技术开始,通过无序介孔二氧化硅载体的后合成改性,合成了两种用于选择性环氧化的铌(V)-二氧化硅催化剂。在含水H 2 O 2存在下,将接枝的Nb / SiO 2固体用作催化剂,用于精细和特殊化学的目标不饱和环状和萜烯化合物的环氧化,特别是:环己烯,1-甲基环己烯,柠檬烯,香芹酚,α-萜品醇,异戊醇,香蒲醇,香芹酮以及角鲨烯和乙酸异戊酯。这些催化剂在较短的反应时间(低至1小时)中也显示出高收率(最高73%)和对所需环氧化物的优异化学选择性(最高98%)。
Mitsunobu Reaction of Unbiased Cyclic Allylic Alcohols
作者:Brian K. Shull、Takashi Sakai、Jeffrey B. Nichols、Masato Koreeda
DOI:10.1021/jo9615155
日期:1997.11.1
nature of the starting allylic alcohol does not appear to affect the product distribution for this reaction, nor does methyl substitution at the central carbon of the allylic alcohol. In all cases, significant amounts (8-28%) of non-S(N)2 type products were detected for these sterically unbiased allylic alcohols; only 72-77% of the product was from S(N)2 type reaction when sterically undemanding (R