<b>Diastereoselective Reaction of Buta-1,3-diene with Chiral Derivatives of Glyoxylic Acid: Effective Route to Optically Pure 2-Substituted 3,6-Dihydro-2</b>
<b><i>H</i></b>
<b>-pyrans</b>
The influence of Lewis acids on the diastereoselectivity of [4+2] cycloaddition of buta-1,3-diene (4) to N-glyoxyloyl-(2R)-bornane-10,2-sultam (6a) and (R)-8-phenylmenthyl glyoxylate (6b) was investigated and found to have high levels of asymmetric induction. The highest asymmetric induction (ca. 100% de) was obtained for the reaction of 4 with 6b carried out in toluene and in the presence of chelating
A Concise and Efficient Synthesis of Spiroketals - Application to the Synthesis of SPIKET-P and a Spiroketal from<i>Bactrocera</i>Species
作者:Loic Tomas、Benjamin Bourdon、Jean Claude Caille、David Gueyrard、Peter G. Goekjian
DOI:10.1002/ejoc.201201199
日期:2013.2
We report the synthesis of spiroketals by sequence of enolethersynthesis and cyclization. The enolethers were prepared from lactones by a Julia olefination reaction, and the starting chiral lactone was prepared from an industrial intermediate. This route is a concise and efficient way to synthesize naturally occurring and biologically interesting spiroketals. We used this sequence for the preparation
我们通过烯醇醚合成和环化的顺序报告了螺缩酮的合成。烯醇醚由内酯通过 Julia 烯化反应制备,起始手性内酯由工业中间体制备。该路线是合成天然存在且具有生物学意义的螺旋酮的简洁有效的方法。我们使用这个序列来制备 SPIKET-P 和来自 Bactrocera 物种的 SPiroketal。
Synthesis of Some Isoxazolidine and Isoxazoline Derivatives Using Nitrone-Derived (‒)-Menthone via 1,3-Dipolar Cycloaddition with Alkenes, Alkynes and Cycloalkenes
Cycloaddition reactions between a menthone-based chiral nitrone and alkenes or alkynes under microwave activation afforded a series of enantiopure cycloadducts in good yields and with high stereo selectivity. Removal of the chiral auxiliary under acid-catalysis led to a new series of isoxazolidines and isoxazolines with the control of one, two or three stereogenic centers.
Asymmetric hetero Diels-Alder reactions and ene reactions catalyzed by chiral copper(II) complexes
作者:Mogens Johannsen、Karl Anker Joergensen
DOI:10.1021/jo00123a007
日期:1995.9
A new copper(II) bisoxazoline-catalyzed reaction of glyoxylate esters with dienes leading to the hetero Diet-Alder product and the ene product in high yield and with a high enantiomeric excess (ee) has been developed. The hetero Diels-Alder product:ene product ratio is in the range 1:0.6 to 1:1.8 and is dependent on both the chiral ligand attached to the metal, the glyoxylate ester, and the reaction temperature. The scope of the copper(II) bisoxazoline-catalyzed reaction of glyoxylate esters with dienes is demonstrated by the reaction of a variety of different dienes with ethyl and isopropyl glyoxylate, and it is shown that a simple substrate such as 1,3-butadiene reacts to give the hetero Diels-Alder product in 55% yield with an ee of 87%. Furthermore, the synthetic application of the reaction is demonstrated by the synthesis of a highly interesting synthon for sesquiterpene lactones in high yield and diastereoselectivity, and with a very high ee from 1,3-cyclohexadiene and ethyl glyoxylate using a copper(II) bisoxazoline as the catalyst. A mechanism for the hetero Diels-Alder reaction, which accounts for the enantioselectivity in the reactions, is proposed.
Highly diastereoselective hetero-Diels–Alder reaction of buta-1,3-diene with N-glyoxyloyl-(2R)-bornane-10,2-sultam: an efficient synthesis of homochiral (S)-3-[2-{(methylsulfonyl)oxy}ethoxy]-4-(triphenylmethoxy)-1-butanol methanesulfonate
The influence of Lewis acid on the diastereo selectivity of [4+2] cycloaddition of buta-1,3-diene to N-glyoxyloyl-(2R)-bornane-10,2-sultam was investigated and high levels of asymmetric induction were achieved. (S)-3-[2- (Methylsulfonyl)oxy}ethoxyl-4-(triphenylmethoxy)-1-butanol methanesulfonate were synthesized in 15% overall yield, applying as a crucial step the above-mentioned [4+2] cycloaddition catalyzed by ZnBr2. (C) 2003 Elsevier Science Ltd. All rights reserved.