Concurrent Induction of Two Chiral Centers from Symmetrical 3,4-Disubstituted and 3,3,4-Trisubstituted 4-Pentenals Using Rh-Catalyzed Asymmetric Cyclizations
作者:Masakazu Tanaka、Masanori Imai、Masakazu Fujio、Eishi Sakamoto、Miyuki Takahashi、Yasuko Eto-Kato、Xiao Ming Wu、Kazuhisa Funakoshi、Kiyoshi Sakai、Hiroshi Suemune
DOI:10.1021/jo000781m
日期:2000.9.1
Asymmetric cyclization of symmetrical 3,4-disubstituted and 3,3, 4-trisubstituted 4-pentenals was studied using Rh-complexes with chiral ligands. The cyclization of symmetrical 4-pentenals 4a,b by a neutral Rh[(R)-BINAP]Cl afforded cis-3,4-disubstituted (4R)-cyclopentanones 9a,b of >95% ee in 25-31% yields; on the other hand, the cyclization of 4a-c by a cationic Rh[(R)-BINAP]ClO(4) afforded trans-3
使用具有手性配体的Rh-络合物,研究了对称的3,4-二取代和3,3,4-三取代的4-戊烯的不对称环化。用中性的Rh [(BIN)] Cl将对称的4-戊烯醛4a,b环化,得到ee> 95%ee的顺式-3,4-二取代的(4R)-环戊酮9a,b,产率为25-31%。另一方面,阳离子Rh [[BINAP] ClO(4)对4a-c的环化作用在70-ee中提供了95%ee以上的反式-3,4-二取代(4S)-环戊酮10a-c。产率81%。所有立体异构体都可以通过选择中性或阳离子Rh-络合物和(R)-或(S)-BINAP配体来立体选择性地制备。Rh催化的环化反应可用于带有手性季碳的环戊酮17和18的构建。阳离子Rh [(R)-BINAP] ClO(4)的环化反应提供了光学活性的反式3,3,ee为92-95%的4-三取代环戊酮18a-c,产率为75-83%。还使用氘醛对催化循环进行了研究,并提出了对映体和非对映体的初步机理。