【摘要】 <正> 本文首次报道镁对3-氯-2-烃基四氢呋喃(1)的开环反应,制得一系列4-烃基-3-丁烯-1-醇(2)。反应平稳、安全、产率高,立体选择性亦较强。反式1开环时,所得反式2的纯度达99.9%;顺式1开环时,所得顺式2的纯更多还原

【Abstract】 This paper reports the ring scission of2-alkyl-3-chlorotetrahydrofurans (1) bymagnesium,leading to the formation of aseries of 4-alkyl-3-buten-1-ols (2):(?)R=Me(a),Et(b),n-Pr(c),i-Pr(d),n-Bu(e),t-Bu(f),n-Pentyl(g),Ph(h),Bz(i)The ring scission of 1 by sodium wasreported in literature,but the reaction hasmany disadvantages,which are overcomedby using magnesium instead of sodium.Furthermore,magnesium ring scissionsof 1 lead to high yield of 2,with high ste-reoselectivity for the formation of E-2 orZ-2 as compared with sodium.For example,in the ring scission of cis-1b by sodium,there was obtained 83% yield of 2b,con-sisting of 49% E-isomer and 51% Z-iso-mer (leaf alcohol),whereas the ring scis-sion of cis-1 b by magnesium increased theyield (95%) of 2 b,consisting of 15% E-isomer and 85% Z-isomer.The ring scis-sion of trans-1 by magnesium gave mainlythe E-isomers of 2 a-2 i (～99.9%) withalso high yield.As the compounds 2 a～2 ipossess the structural feature of many na-tural products,such as perfumes and insectsex pheromones,and the compounds 1 canbe obtained easily by the intereaction of aGrignard reagent and 2,3-dichlorotetrahy-drofuran,so the ring scission of 1→2 bymagnesium offers a convenient and usefulapproach to the above natural products.Fur-thermore,primary alcohols 2 can be easilyconverted to bromides and the correspondingGrignard reagents,which can in turn reactfurther with the 2,3-dichlorotetrahydro-furan,thus offering a good method of leng-thening the chain of a given molecule asneeded.General procedure0.06 mol of magnesium (99%.Fe,0.029%) was added to 0.05 mol of cis- ortrans-2-alkyl-3-chloro-tetrahydrofuran in 20mL anhydrous ether.The mixture was stirredat room temperature (25℃) for 4 h,hydroly-zed with dilute hydrochloric acid.The or-ganic layer was separated and the aqueouslayer extracted with ether.The solution wasdried and distilled to give the product.Theresults are given in table 1.更多还原