Catalytic Asymmetric Intramolecular Aminopalladation:  Enantioselective Synthesis of Vinyl-Substituted 2-Oxazolidinones, 2-Imidazolidinones, and 2-Pyrrolidinones

Abstract

A new catalytic asymmetric synthesis of five-membered nitrogen heterocycles is reported. This synthesis employs ferrocenyloxazoline palladacycles (FOP trifluoroacetate catalysts) 2 and 4 and proceeds by a catalytic cycle involving Pd(II) intermediates. For example, prochiral (Z)-4-acetoxy-2-buten-1-ols are condensed with an arylsulfonyl isocyanate and the derived allylic N-arylsulfonylcarbamates cyclize in situ upon addition of 0.5-5 mol % of 2 or 4 to form 4-vinyloxazolidin-2-ones 6, 13, and 15 in high yield and 89-99% ee. The related 2-pyrrolidinone 19 and 2-imidazolidinone 18 are prepared in similar fashion. Pyrrolidinone 19 can be converted in two steps to the unnatural enantiomer of the GABA inhibitor vigabatrin 20.

Synthesis and structural characterization of enantiopure exo and endo six-membered oxazoline-derived palladacycles

“…Recently, a number of C * -chiral enantiopure exo [48][49][50], endo [48,[50][51][52][53][54][55][56][57][58][59][60][61][62] and pincer-type [58,[63][64][65][66][67][68][69][70] cyclopalladated oxazolines with a five-membered metalacycle have been reported (Chart 2). Other cyclopalladated oxazolines with planar and central chirality have also been studied [38,[71][72][73][74][75][76][77][78][79][80]. It has also been shown that the formation of five-membered oxazolinederived metalacycles complies with the endo rule: the preference of endo palladation over exo [48,50].…”

Synthesis, characterization and crystal structures of two cis/trans pyridine-cyclopalladated ferrocenylimine complexes

“…The most common palladacycles are derived from organic molecules containing N-donor groups such as tertiary amines and imines with a five or six-membered chelate. Among them, cyclopalladated ferrocene derivatives are particularly interesting since planar chirality may be introduced in the 1,2-disubstituted ferrocene moiety which shows great potential in asymmetric synthesis and catalysis [5,6]. In this respect, we have reported a variety of achiral and chiral cyclopalladated complexes having Schiff base type of ferrocenylimine ligands [7][8][9][10][11] and found that some cyclopalladated complexes are efficient catalysts for the Heck [9] and Suzuki reactions [10,11].…”

Palladacycle‐Catalyzed Tandem Allylic Amination/Allylation Protocol for One‐Pot Synthesis of 2‐Allylanilines from Allylic Alcohols

“…Palladacycles have attracted much attention in the homogeneous catalysis of reactions such as cross-coupling, [21] allylic amination, [22] allylic rearrangement [23] and so on. We have previously explored the use of palladacycles for the asymmetric Claisen rearrangement reaction [24] and also investigated their potential in C À N bond formation scenarios such as hydroamination.…”