Preparation of Chiral Amine Carbonyl Chromium(0) Complexes with [(Norbornadiene)Cr(CO)4] as the Complexation Reagent

The complexation of an arene to a chromium tricarbonyl unit changes its chemical behavior, giving rise to unprecedented transformations. The electron-withdrawing effect of the unit allows efficient nucleophilic attack (S(N)Ar and dearomatization reactions), stabilizes negative charges in benzylic positions and activates C(Ar)-halogen bonds for cross-coupling reactions. In addition, the Cr(CO)(3) moiety exerts great facial control so it can be used as an auxiliary that can easily be removed. The 1,2- and 1,3-unsymmetrically disubstituted complexes are planar chiral and there are various ways to prepare them in enantiomerically pure form. Planar chiral chromium complexes are becoming useful intermediates and ligands for asymmetric catalysis. This mature field of organometallic chemistry has given rise to several synthetic applications of chromium arene complexes in the synthesis of natural products. This chemistry is overviewed in this tutorial review, giving special attention to the most recent and outstanding contributions in the area.

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“…Unfortunately, they achieved negligible de in the reactions with a number of chiral arenes (Scheme 5). 7…”

Section: Renewable Chiral Auxiliariesmentioning

confidence: 99%

Chromium arene complexes in organic synthesis

2007

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“…These new species could then, in turn, be used as complexation agents for arenes, but significant amounts of chirality transfer were not observed. 50 As a substituent, [CrPh(CO) 3 ] efficiently stabilises both propargyl cations and anions. In the subsequent trapping reactions, studied for the anionic species, the regioselectivity depends upon the hardness of the attacking electrophile.…”

Section: Organometallics and Carbon-donor Ligandsmentioning

confidence: 99%

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Malito

2001

Annu. Rep. Prog. Chem., Sect. A

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“…Although all a-alkylated sulfonamides 4 were obtained in unsatisfactory diastereoselectivities, it was observed that better diastereoisomer excesses (de) could be obtained when the steric demand of the side chain at the pyrrolidine ring was increased. We then turned to the readily available amine auxiliary (4S,5S)-2,2-dimethyl-4-phenyl-1,3-dioxan-5-anine ((S,S)-5), which has already been applied in a series of auxiliarycontrolled reactions [9] or in the preparation of a chiral ligand for chromium(0) complexes [10]. (S,S)-5 was converted to the tertiary N-methylsulfonamide (S,S)-7 in two steps via the secondary derivative (S,S)-6 and subsequent N-methylation (Scheme 2).…”

mentioning

confidence: 99%

Asymmetric Synthesis of -Substituted N-Methylsulfonamides

Enders¹,

Thomas²,

Vignola³

et al. 2002

HCA

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Dedicated to Professor Dieter Seebach on the occasion of his 65th birthday A novel amine auxiliary for the asymmetric synthesis of a-substituted N-methylsulfonamides is described. The reaction of 4-([1,1'-biphenyl]-4-yl)-2,2-dimethyl-1,3-dioxan-5-amine (16) with various aliphatic sulfonyl chlorides afforded the corresponding sulfonamides, which were lithiated and subsequently reacted with electrophiles to give the corresponding products in high yields and good-to-excellent asymmetric inductions (de 83 ± 95%). Racemization-free cleavage of the auxiliary led to the a-alkylated N-methylsulfonamides in acceptable yields and high enantiomer purities (ee 91 to ! 98).

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Preparation of Chiral Amine Carbonyl Chromium(0) Complexes with [(Norbornadiene)Cr(CO)4] as the Complexation Reagent

Cited by 5 publications

References 69 publications

Chromium arene complexes in organic synthesis

Chromium arene complexes in organic synthesis

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Asymmetric Synthesis of -Substituted N-Methylsulfonamides

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