FORMATION OF DELTA-4-OXOCENES FROM LEWIS ACID PROMOTED CYCLIZATIONS OF 5-HEXENYL ACETALS - EVIDENCE FOR A CONCERTED ENE CYCLIZATION MECHANISM

被引：62

作者：

BLUMENKOPF, TA ^{[1
]}

LOOK, GC ^{[1
]}

OVERMAN, LE ^{[1
]}

机构：

[1] UNIV CALIF IRVINE,DEPT CHEM,IRVINE,CA 92717

来源：

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY | 1990年 / 112卷 / 11期

关键词：

D O I：

10.1021/ja00167a042

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

Both the intermolecular (kinetic) and intramolecular (product) hydrogen-deuterium isotope effects were determined to be 1.65 for the formation of 2-methyl-4-(trimethylsilyl)-Δ4-oxocene (20) from the SnCl4-promoted cyclization of acetals 19, 30, and 31 (eq 6). In other experiments silyl acetal 32 was found to cyclize in the presence of SnCl4 to form the silyl-Δ4-oxocene 34 and the alkylideneoxepane 35 in 2:1 ratio (eq 7). Both results provide strong evidence that the formation of 4-(trimethylsilyl)-Δ4-oxocenes from SnCl4-promoted cyclizations of 5-(trimethylsilyl)-5-hexenyl acetals takes place by a concerted intramolecular ene mechanism. Also reported are SnCl4-promoted exchange reactions of formaldehyde and aldehyde-derived acetals, which occur readily at-10 to 0 °C and-70 °C, respectively (eqs 2 and 3). © 1990, American Chemical Society. All rights reserved.

引用

页码：4399 / 4403

页数：5

共 42 条

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