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近年来,有机合成技术有很大进步,主要表现在出现了大量新反应和新试剂。它们具有产率好、反应条件温和、选择性和立体定向性高等优点,使有机合成功效大大提高。最近许多结构复杂的天然产物如维生素B_(12)和各种前列腺素的合成可以说与这些新合成手段的使用是分不开的。本文选择其中在有机合成中应用较多,而所需条件又是普通有机实验室中容易办到的一些,作一简单介绍。还原1.新的氢化催化剂过去经常使用的催化剂如亚当斯氧化铂催化剂和兰尼镍等制备都颇麻烦。近年来,发现一些新的催化剂,不但制法远为简便,而且性能上也比过去的更为优越。将氯铂酸在乙醇中用硼氢钠还原,立即生成黑色金属铂沉淀。这样生成的铂作为氢化的催化剂,活性比亚当斯氧化铂催化剂更强。最近,又有报导用三乙基硅烷还原氯铂酸所生成的铂催化剂,性能比用硼氢钠还原生成的更好。将醋酸镍在水中用硼氢钠还原,立即生成黑色粒状物。其组成现还不很清楚,可能是一种硼化镍。其简称为 p-1 Ni,用作氢化催化剂,活性比兰尼镍更强,而且反应时异构化(双键移动)的副作用大为减少。
In recent years, organic synthesis technology has made great progress, mainly in the emergence of a large number of new reactions and new reagents. They have the advantages of good yield, mild reaction conditions, high selectivity and high stereospecificity, which greatly increases the efficiency of organic synthesis. Recently, the synthesis of many complex natural products such as vitamin B 12 and various prostaglandins can be said to be inseparable from the use of these new synthetic means. This article chooses which of the more used in organic synthesis, and the required conditions are common to some organic laboratory can be done for a brief introduction. Reduction 1. New Hydrogenation Catalyst Conventionally used catalysts such as Adams Platinum catalyst and Raney Nickel and other preparations are quite troublesome. In recent years, we have found some new catalysts that are not only far simpler but also superior in performance than in the past. The chloroplatinic acid was reduced with sodium borohydride in ethanol to immediately form a black metal platinum precipitate. The platinum thus formed is more active as a hydrogenation catalyst than Adams platinum oxide catalyst. Recently, it has also been reported that reduction of chloroplatinic acid with triethylsilane produces a platinum catalyst which produces better performance than sodium borohydride. Nickel acetate was reduced with sodium borohydride in water to produce black granules immediately. Its composition is still not clear, it may be a nickel boride. Its abbreviation is p-1 Ni, which is used as a hydrogenation catalyst. Its activity is stronger than that of Raney nickel, and the side effects of isomerization (double bond shift) are greatly reduced during the reaction.