Neighboring group participation in Lewis acid-promoted [3 + 4] and [3 + 5] annulations. The stereocontrolled synthesis of tricyclic ethers
摘要:
A variety of 1,4- and 1,5-keto aldehydes derived from cycloalkanes are coupled with the bis(trimethylsilyl) enol ether of methyl acetoacetate in the presence of either TMSOTf or TrSbCl6 to generate tricyclic ethers. The reactions proceed with excellent regiochemical control by a mechanism involving neighboring group participation. This mechanism involves initial formation of a bicyclic oxocarbenium ion intermediate from the keto aldehyde substrates. The geometries of selected bicyclic intermediates have been optimized using the AM1 method allowing successful prediction of the stereochemical outcomes in the cyclization in most cases. Epimerization of alpha-chiral keto aldehyde substrates does not appear to occur in these Lewis acid-promoted annulation reactions.
Neighboring group participation in Lewis acid-promoted [3 + 4] and [3 + 5] annulations. The stereocontrolled synthesis of tricyclic ethers
摘要:
A variety of 1,4- and 1,5-keto aldehydes derived from cycloalkanes are coupled with the bis(trimethylsilyl) enol ether of methyl acetoacetate in the presence of either TMSOTf or TrSbCl6 to generate tricyclic ethers. The reactions proceed with excellent regiochemical control by a mechanism involving neighboring group participation. This mechanism involves initial formation of a bicyclic oxocarbenium ion intermediate from the keto aldehyde substrates. The geometries of selected bicyclic intermediates have been optimized using the AM1 method allowing successful prediction of the stereochemical outcomes in the cyclization in most cases. Epimerization of alpha-chiral keto aldehyde substrates does not appear to occur in these Lewis acid-promoted annulation reactions.
Novel differences between the solid state and solution phase photochemistry of 1,2-cyclodecanedione
作者:Gunnar Olovsson、John R. Scheffer、James Trotter、Chung-Hsi Wu
DOI:10.1016/s0040-4039(97)01657-2
日期:1997.9
1,2-Cyclodecanedione (1) undergoes a novel photorearrangement in the crystalline state that is different from the Norrish/Yang type II photocyclization process observed in solution. A possible mechanism is presented and discussed.
1,2-环十二烷二酮(1)在晶体状态下发生新的光重排,这与溶液中观察到的Norrish / Yang II型光环化过程不同。提出并讨论了一种可能的机制。
Neighboring group participation in Lewis acid-promoted [3 + 4] and [3 + 5] annulations. The stereocontrolled synthesis of tricyclic ethers
作者:Gary A. Molander、Kimberly O. Cameron
DOI:10.1021/jo00074a018
日期:1993.10
A variety of 1,4- and 1,5-keto aldehydes derived from cycloalkanes are coupled with the bis(trimethylsilyl) enol ether of methyl acetoacetate in the presence of either TMSOTf or TrSbCl6 to generate tricyclic ethers. The reactions proceed with excellent regiochemical control by a mechanism involving neighboring group participation. This mechanism involves initial formation of a bicyclic oxocarbenium ion intermediate from the keto aldehyde substrates. The geometries of selected bicyclic intermediates have been optimized using the AM1 method allowing successful prediction of the stereochemical outcomes in the cyclization in most cases. Epimerization of alpha-chiral keto aldehyde substrates does not appear to occur in these Lewis acid-promoted annulation reactions.