Studies Dealing with Thionium Ion Promoted Mannich Cyclization Reactions
作者:Albert Padwa、Alex G. Waterson
DOI:10.1021/jo991414h
日期:2000.1.1
six-membered alkylthio-substituted lactams as transient intermediates. Further reaction of the alkylthio-substituted lactam with DMTSF generates an N-acyliminium ion, which undergoes cyclization with the tethered aromatic ring to produce an azapolycyclic ring system. Related cyclization sequences occur when amido thioacetals possessing simple olefinic tethers were used. The overall procedure represents an efficient
Cyclisation of acetylenic ethoxylactams 1b-12b leads to bridgehead nitrogen bicyclic ketones in excellent yields. The reaction is weakly acid-catalysed and proceeds at ambient temperature. The observed regioselectivity effect is discussed in terms of stability of exo vs endo vinylcations and ring strain effects. The high yield conversion of N-(5-hexynyl)-ethoxy lactams 7b and 8b in the 5/8 and 6/8
Gold(I)-Catalyzed Hydroaminaloxylation and Petasis–Ferrier Rearrangement Cascade of Aminaloalkynes
作者:Amol B. Gade、Nitin T. Patil
DOI:10.1021/acs.orglett.6b00585
日期:2016.4.15
An efficient method has been developed to generate a diverse array of indolizidines and quinolizidines from readily available aminaloalkynes via a gold(I)-catalyzed hydroaminaloxylation and Petasis–Ferrier rearrangement cascade. The method enabled a formal synthesis of (±)-antofine.
The cyclization of α-N-acyliminium ions generated from ethoxylactams 1–3 using trifluoroacetic acid, trifluoromethanesulfonic acid and anhydrous HF affords ketones, bromoalkenes and geminal bromofluoro compounds, respectively. A non concerted process explains these results which demonstrate the high reactivity of the intermediate bromocarbenium ions with different nucleophiles. The unexpected fluorination