Erythro-selective aldol reaction via tris(dialkylamino)sulfonium enolates
Erythro-selective aldol reaction via tris(dialkylamino)sulfonium enolates
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通过三(二烷基氨基)锍烯醇化物的红选择性羟醛反应
DOI：
10.1021/ja00398a047
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发表时间：
1981
影响因子：
15
通讯作者：
J. Sakata
中科院分区：
文献类型：
--
作者：
R. Noyori;I. Nishida;J. Sakata
使RCHO醚2、醛（1.1-1.4当量）和催化量（0.01-0.1当量）的TAS二氟三甲基硅醇酯（3）7在THF中在低温下静置，获得相应的β-三甲基甲硅烷氧基酮6。在某些情况下，需要添加过量的甲硅烷基氟化物4（最多10当量）以高产率获得6。用稀盐酸除去甲硅烷基，得到β-羟基酮。通过1H NMR进行立体化学归属（苏型或赤型8），特别是使用公认的7threo> Jcrnthr 0关系。10一些代表性的反应总结在表I中。作为主要产物获得的双羟醛醇是动力学控制的产物。氟离子催化的环戊酮末端的甲硅烷基醚和异丁醛在-78 ℃下的反应几乎完全产生双加成物（条目2）。在这些反应条件下，没有明显的邻位到苏型异构化;苏型对应物也没有异构化。当反应温度升高时，反应的立体选择性有所降低
RCHO ether 2, an aldehyde (1.1-1.4 equiv), and a catalytic amount (0.01-0.1 equiv) of TAS difluorotrimethylsiliconate (3) 7 in THF was allowed to stand at low temperatures, the corresponding/3-trimethylsiloxy ketone6 was obtained. In some cases addition of an excess amount of the silyl fluoride 4 (up to 10 equiv) was required to obtain 6 in high yield. Removal of the silyl group with dilute hydrochloric acid afforded the/3-hydroxy ketone. The stereochemical assignment (threo or erythro8) was made by ‘H NMR, particularly using the well-accepted 7threo> Jcr „thr0 rela-tionship. 10 Some representative reactions are summarized in Table I.The erythro aldols obtained as the major product were kinet-ically controlled ones. The fluoride ion catalyzed reaction of cyclopentanone end silyl ethers and isobutyraldehyde at-78 C produced the erythro adduct almost exclusively (entry 2). Under these reaction conditions, there was no apparent erythro to threo isomerization; the threo counterpart did not isomerize either. When the reaction was carried out at an elevated temperature, the degree of the stereoselectivity was reduced to some extent