在这里,我们描述了N-磺酰基-1,2,3-三唑的铑催化桥接 (3+2) 环加成级联反应,这使得各种功能化和合成具有挑战性的桥接环系统的有效非对映选择性构建成为可能。这种简单、直接的转化具有广泛的底物范围和出色的官能团耐受性。使用该方法有效地合成了果糖苷的高应变多环双环[2.2.2]octa[ b ]吲哚核。
在这里,我们描述了N-磺酰基-1,2,3-三唑的铑催化桥接 (3+2) 环加成级联反应,这使得各种功能化和合成具有挑战性的桥接环系统的有效非对映选择性构建成为可能。这种简单、直接的转化具有广泛的底物范围和出色的官能团耐受性。使用该方法有效地合成了果糖苷的高应变多环双环[2.2.2]octa[ b ]吲哚核。
Facile Synthesis of Aliphatic Esters, Malonates and Phenylsulfonyl Esters Using Copper-Catalyzed Addition of Methallyl Grignard Reagent to Activated Cyclopropanes
作者:Igor Prowotorow、Jerzy Wicha、Koichi Mikami
DOI:10.1055/s-2001-9751
日期:——
Copper-mediated conjugate addition of allylic Grignard reagents to activated cyclopropane derivatives was studied. Unsaturated esters, malonates and phenylsulfonyl esters 2a-d were synthesized from the respective cyclopropanes 1a-d and methallylmagnesium chloride.
Iodocarbocyclizationreactions of dimethyl alkenylmalonates in the presence of I2 and Ti(Ot-Bu)4 proceed in a regioselective and stereospecific manner through an ionic mechanism.
The cyclization reactions of dimethyl 4-alkenylmalonate derivatives la-d in the presence Of 12 and Ti(Ot-Bu)4 proceed in a highly regio- and stereocontrolled manner (5-exo cyclization and trans addition) to give (iodoalkyl)cyclopentane derivatives 2 or bicyclic lactones 3 through the displacement of the iodide of 2 by an ester group. Iodocarbocyclization reactions of dimethyl [(cycloalkenyl)alkyl]malonates 1g-i or dimethyl [(methylenecycloalkyl)alkyl]malonates 1j and 1k proceed regio- and stereoselectively to give fused ring compounds or spiro compounds, respectively, as single isomers. Similar reactions of 4-alkynyl derivatives 5 give preferentially E-iodomethylene cyclopentane derivatives 6. An ionic mechanism rather than a radical mechanism is suggested on the basis of the regioselectivity and stereospecificity of the above reactions.