Organolanthanide-catalyzed Cyclization Reactions

Lewis acid-catalyzed ene cyclization reactions at low temperature have been shown to yield substituted piperidines with a high diastereomeric ratio <05TL6611>. Organolanthanide-catalyzed cyclization-silylation has been developed as a powerful strategy for the piperidine rings found in alkaloids. As a prototypical example, the simple diallyl amine 174 was cyclized to 175 in the presence of 5 mol % of the catalyst shown in Scheme 50 and a suitable silane terminator <0512631>. 

Scheme 5-15 Examples of organolanthanide-cat-alyzed hydrophosphina-tion/q clization. Eq. (6) Phosphinoalkenes can undergo organolanthanide-catalyzed hydrophosphi-nation/cyclization to give phospholanes or an uncatalyzed reaction to give phosphorinanes...

Although efficient for the intramolecular hydroamination/cyclization (abbreviated IH below) of aminoalkenes (see below), organolanthanides exhibit a much lower catalytic activity for the intermolecular hydroamination of aUcenes, as exemplified by the reaction of n-PrNH2 with 1-pentene catalyzed by a neodymium complex (Eq. 4.17) [127]. 

Hong S, Kawaoka AM, Marks TJ. Intramolecular hydroami-nation/cyclization of conjugated aminodienes catalyzed by organolanthanide complexes.Scope, diastereo and enantiose-lectivity, and reaction mechanism. J. Am. Chem. Soc. 2003 125(51) 15878-15892. 

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