Asymmetric spirocyclization: A new type of acid-catalyzed intramolecular 1, 4-addition to form carba-spirocyclic compounds
摘要:
Novel spirocyclization based on intramolecular 1,4-addition and its asymmetric version have been developed using a combination of Lewis acid and 1,2-diol. Treatment of five- and six-membered alpha,beta-unsaturated cyclic ketones having a 4-oxopentyl group at the beta-position with Lewis acid and ethylene glycol gave spiro[4.5]decane-2,7-dione and spiro[5.5]undecane-2,8-dione, respectively. The asymmetric version of this reaction has been developed by using optically active 1,2-diol such as cyclohexane-1,2-diol to afford the spirocyclic products of up to 85% e.e. (C) 1998 Elsevier Science Ltd. All rights reserved.
Opening of cyclopropyl ketones with SmI2. Synthesis of spirocyclic and bicyclic ketones by intramolecular trapping of an electrophile
作者:Gary A. Molander、Cristina Alonso-Alija
DOI:10.1016/s0040-4020(97)00499-7
日期:1997.6
A method for the opening of cyclopropyl ketones with samarium(II) iodide followed by the intramolecular trapping of an electrophile is described. This process leads to the obtainment of functionalized spirocyclic, bicyclic, and tricyclic ketones in moderate to good yields.
Rhodium(II)-carbenoid C–H insertion reactions in the synthesis of β-oxospirane systems
作者:Pompiliu S. Aburel、Kjell Undheim
DOI:10.1039/b001988g
日期:——
A simple one-pot procedure is described for the preparation of spiro[4.4]nonane-2,7-dione derivatives from open chain bis(α-diazoketones) by two consecutive intramolecular Rh(II)-catalyzed carbenoid insertion reactions. With 1-diazo-4-(3-oxocycloalkyl)butan-2-ones as substrates, the methodology provides 2,7-dioxospiranes with a cyclopentane ring spiroannulated onto a five-, six- or seven-membered cycloalkane.