Iridium(<scp>I</scp>)‐Catalysed Tandem Hydrosilylation‐Protodesilylation of Imines

Field, Leslie D.; Messerle, Barbara A.; Rumble, Sarah L.

doi:10.1002/ejoc.200500168

Cited by 30 publications

(14 citation statements)

References 24 publications

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“…Full conversion of the imines required the use of bis -aryl silanes and 5 mol% of the catalyst. Recently reported by the group of Messerle is the more effi cient catalyst (6) (Figure 13.1 ) [8] . This cationic iridium complex bearing a bis(pyrazol -1 -yl)methano ligand gave high activity for the ketimine derived from acetophenone and aniline when 0.5 mol% of catalyst was used with triethylsilane in methanol.…”

Section: Rh Ir Ru Based Catalystsmentioning

confidence: 99%

Hydrosilylation of Imines

Riant¹

2008

Modern Reduction Methods

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13 IntroductionThe fi rst examples of the production of chiral secondary alcohols and amines by the reduction of a carbonyl or imino group using a silane as a reducing agent and a transition metal catalyst was reported during the mid 1970s by Kagan [1] . Following this fi rst report, the literature showed a growing interest in the discovery of effi cient catalytic systems for the hydrosilylation of ketones and aldehydes, while imines only started to show signifi cant advances much later . One of the main reasons is that most of the effi cient catalytic systems for the reduction of ketones were rhodium -based catalysts that usually required activated silanes such as bisaryl silanes. While these systems were active under very mild conditions, they suffered from strong economic drawbacks due to the cost of the catalysts, relatively poor catalytic effi ciency compared to hydrogenation and the cost of the silanes. Imines being poorer substrates than aldehydes and ketones suffered even more from these limitations and were neglected as substrates for hydrosilylation reactions until more effi cient systems were discovered during the 1990s. Indeed, imines are less electrophilic substrates compared to their carbonyl counterparts and are also susceptible to isomerization to enamines , when they posses one or more α -hydrogen. It is, however, possible to increase the electrophilic character of the imino group by the introduction of an aryl or an electron -withdrawing group on the nitrogen. The most common activating groups are tosyl, Boc or diphenylphosphinoyl. However, it is usually considered that only diphenylphosphinoyl combines ease of synthesis, stability to moisture and simplicity of removal for further transformations in synthesis. When designing a chiral catalyst for enantioselective addition of a nucleophile on an aldimine or a ketimine, another diffi culty arises from the possible cis -trans isomerization of the C = N double bond.However, nucleophilic addition to imines remains an attractive method for the synthesis of amines and increasing numbers of examples in the fi eld of asymmetric catalysis have been reported during the since the 1990s [2] . Concerning reduction processes, the costs of the catalytic systems and the silanes have often drawn chemists to develop more economic alternatives, such as hydrogenation.

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Section: Rh Ir Ru Based Catalystsmentioning

confidence: 99%

Hydrosilylation of Imines

Riant¹

2008

Modern Reduction Methods

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“…for the hydrosilylation of N-arylketimines, with the turnover frequency up to 5000 h -1 . 44 Similarly, Djukic et al have described in 2012 the use of chromium tricarbonyl coordinated iridacycle C19a (2.5 mol%) for the reduction of aromatic imines using 1.3 equiv. of Et 3 SiH in methanol at 25 °C for 2-3 h leading quantitatively to the corresponding amines.…”

Section: B5 Group 9 (Iridium and Rhodium) Catalystsmentioning

confidence: 99%

Amine synthesis via transition metal homogeneous catalysed hydrosilylation

2016

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International audienceAmines are among the most important compounds due to their wide applications in several areas of importance. Among the numerous synthetic methodologies, this review provides a comprehensive summary of the preparation of amines involving homogeneous transition metal catalysed hydrosilylation methodologies including the reduction of imine, amide, nitro and nitrile derivatives. In addition, challenging tandem reactions such as reductive amination or the use of CO2 as a C-1-building block in N-methylation of amines will also be discussed

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“…To further extend the utility of the indolenine template, we report herein a general and convenient one-pot synthesis of 3,3-disubstituted indolines 5, which allows introduction of substitution at essentially any position of the molecule. Although sporadic synthesis of indolines from their corresponding indolenines have been previously reported, [36][37][38][39][40][41] the examples were generally limited to 3,3-dimethylindolines and the synthesis required isolation of relatively instable indolenines.…”

Section: Introductionmentioning

confidence: 99%