Novel triethylsilane mediated reductive N -alkylation of amines: improved synthesis of 1-(4-imidazolyl)methyl-4-sulfonylbenzodiazepines, new farnesyltransferase inhibitors

Chen, Bang‐Chi; Sundeen, Joseph E.; Guo, Peng; Bednarz, Mark S.; Zhao, Rulin

doi:10.1016/s0040-4039(00)02257-7

Cited by 82 publications

(32 citation statements)

References 6 publications

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“…This method employs the inexpensive triethylsilane as the reducing agent and was later used by Chen et al . for the N -alkylation of benzodiazepine derivatives [42] . A straightforward " one pot " amination of various aldehydes and ketones with primary and secondary amines was proposed by the group of Chandrasekhar, who used a combination of titanium(IV) isopropoxide and PMHS for the reductive amination [43] .…”

Section: Miscellaneous Methodsmentioning

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: Miscellaneous Methodsmentioning

confidence: 99%

Hydrosilylation of Imines

Riant¹

2008

Modern Reduction Methods

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“…Subsequent reduction with borane afforded 2 a, and a subsequent copper-catalyzed cyanation resulted in 2 b. Selective N-sulfonylation with 4-methoxybenzenesulfonyl chloride in pyridine and reductive amination with 4-imidazocarbox- aldehyde in the presence of trifluoroacetic anhydride (TFAA) as a water scavenger [12] resulted in building blocks 3 a and 3 b in 38 and 26 % overall yield, respectively. Substituents meant to target the hydrophobic binding pocket (R 2 ) were attached by alkylation or aminocarbonylation, (Scheme 2, compounds 4-7).…”

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confidence: 99%

Structure‐Guided Development of Selective RabGGTase Inhibitors

et al. 2011

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“…13 the most often used reagents for this purpose ( Table 1, entry 8 and 12). However, in order to examine a wider range of amines and to better illustrate the scope and limitation of this method, we investigated the reaction with both primary and secondary amines such as benzylamine, piperidine, pyrrolidine and morpholine using PhCHO as a representative aldehyde, and cyclohexanone as a representative ketone (Table 1, entries [13][14][15][16][18][19][20]. Reductive amination of aliphatic aldehyde, such as butanal with aniline also gives excellent yield of corresponding amine (Table 1, entry 23).…”

Section: Resultsmentioning

confidence: 99%

“…2 A variety of reducing agents, such as hydrogen in the presence of metal catalysts, 3 NaBH3CN, 4 NaBH(OAC)3, 5 silica gel-Zn(BH4)2, 6 Ti(O-i-Pr)4-NaBH4, 7 NaBH4-H2SO4, 8 NaBH4-ZrCl 4 , 9 NaBH 4 -NiCl 2 , 10 NaBH 4 -wet-clay-microwave, 11 pyridine-BH3, 12 NaBH4-H3BO3, 13 Zr[(BH4)2(Cl)2(dabco)2], 14 Et3-SiH-CF3CO2H, 15 NaBH4 in micellar media, 16 zinc borohydride N-methyl piperidine, 17 NaBH4-H3PW12O40, 18 NaBH4-Silica phosphoric acid, 19 zinc borohydride N-methyl pyrrolidine 20 NaBH4-Silica-Gel-supported sulfuric acid, 21 NaBH4-Amberlyst 15 22 and NaBH 4 -silica chloride 23 have been developed. However, most of these methods suffer from one or more drawbacks.…”

Section: Introductionmentioning

confidence: 99%