Stereoselective Substitution in 2-Bromo Amides in the Presence of Ag+ or Ag2O
摘要:
Bromine displacement by a primary, secondary, or tertiary amine, or methanol, in chiral nonracemic (S)-2-bromopropanamides 1 occurs with high yields and stereo selectivity. Soluble Ag+ promotes inversion, and solid Ag2O promotes retention of configuration. However, in the case of Et(3)N, Ag+ promotes retention. With the hindered 2-bromo-2-methylbutanamide 5, the displacement by a primary or secondary amine or methanol occurs only in the presence of Ag2O, possibly with retention of configuration.
Mutual kinetic resolution of 3-methyl-3,4-dihydro-2H-1,4-benzoxazines and 2-alkoxyacyl chlorides
作者:Sergey A. Vakarov、Dmitry А. Gruzdev、Liliya Sh. Sadretdinova、Mikhail I. Kodess、Andrey A. Tumashov、Evgeny B. Gorbunov、Galina L. Levit、Victor P. Krasnov
DOI:10.1007/s10593-018-2286-y
日期:2018.4
Stereoselective acylation of racemic 3-methyl-3,4-dihydro-2Н-1,4-benzoxazine and its 7,8-difluoro-substituted analog with racemic 2-alkoxyacyl chlorides was stidied. The reactions of 3-methyl-3,4-dihydro-2H-1,4-benzoxazines with 2-methoxyisopentanoyl chloride were found to be more selective (selectivity factor s 31–32) compared to the acylation with other studied propanoyl chlorides (s 18–21). This
的立体选择性酰化外消旋3-甲基-3,4-二氢-2- Н -1,4-苯并恶嗪及其与外消旋2-烷氧基酰基氯化物-7,8-二氟取代的类似物,stidied。发现3-甲基-3,4-二氢-2 H -1,4-苯并恶嗪与2-甲氧基异戊酰氯的反应比与其他已研究丙酰氯的酰化反应具有更高的选择性(选择性系数s 31–32)(š 18-21)。该事实可能是由于与衍生自丙酸的试剂中的甲基相比,酰氯中的异丙基取代基引起了明显的位阻。
Trennung von Diastereomeren
申请人:BAYER AG
公开号:EP0242778A1
公开(公告)日:1987-10-28
Es wird ein neues Verfahren zur Trennung von Diastereomeren bereitgestellt. Das Verfahren ist dadurch gekennzeichnet, daß man mit Hilfe der Extraktivdestillation unter Zusatz eines Hilfsstoffes arbeitet.
Das Verfahren ist vorzugsweise zur Trennung cyclischer diastereomerer Verbindungen geeignet.