The Give and Take of Alcohol Activation

Watson, Andrew J. A.; Williams, Jonathan M. J.

doi:10.1126/science.1191843

Cited by 624 publications

(215 citation statements)

References 19 publications

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“…Therefore the development of efficient catalytic methodologies for C-N bond formation is a paramount goal in organic chemistry 4 . One of the most important processes to make amines is the Pd-catalysed Buchwald-Hartwig amination 5,6 .…”

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confidence: 99%

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Iron catalysed direct alkylation of amines with alcohols

2014

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The selective conversion of carbon-oxygen bonds into carbon-nitrogen bonds to form amines is one of the most important chemical transformations for the production of bulk and fine chemicals and pharma intermediates. An attractive atom-economic way of carrying out such C-N bond formations is the direct N-alkylation of simple amines with alcohols by the borrowing hydrogen strategy. Recently, transition metal complexes based on precious metals have emerged as suitable catalysts for this transformation; however, the crucial change towards the use of abundant, inexpensive and environmentally friendly metals, in particular iron, has not yet been accomplished. Here we describe the homogeneous, iron-catalysed, direct alkylation of amines with alcohols. The scope of this new methodology includes the monoalkylation of anilines and benzyl amines with a wide range of alcohols, and the use of diols in the formation of five, six-and seven-membered nitrogen heterocycles, which are privileged structures in numerous pharmaceuticals.

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confidence: 99%

“…The choice of an alcohol 4 as substrate for direct C-N bond formation is highly desirable to produce secondary and tertiary amines and N-heterocyclic compounds (Fig. 1).…”

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Iron catalysed direct alkylation of amines with alcohols

2014

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“…The vial was sealed with a screw cap and removed from the glove box. The vigorously stirred solution was irradiated with blue LED light under table fan cooling for 12 h. After the reaction, the reaction mixture was acidified with saturated NH 4 Cl solution and then neutralized with saturated NaHCO 3 solution. The crude product in the aqueous fraction was extracted with ethyl acetate.…”

Section: Methodsmentioning

confidence: 99%

“…Alkylation and reductive amination reactions are still commonly used to prepare and modify amines, and new methods derived from reductive amination, such as the borrowing hydrogen 3 strategy, have been reported [4][5][6][7] . Nevertheless, the most significant development in amine synthesis has been transition-metal-catalysed C-N coupling of aryl electrophiles (halides and pseudo halides) with amine nucleophiles [8][9][10][11] (Fig.…”

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Decarboxylative C(sp3)–N cross-coupling via synergetic photoredox and copper catalysis

et al. 2018

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A mines are one of the most important structural motifs in pharmaceuticals, agrochemicals and organic materials 1,2 . Alkylation and reductive amination reactions are still commonly used to prepare and modify amines, and new methods derived from reductive amination, such as the borrowing hydrogen 3 strategy, have been reported [4][5][6][7] . Nevertheless, the most significant development in amine synthesis has been transition-metal-catalysed C-N coupling of aryl electrophiles (halides and pseudo halides) with amine nucleophiles [8][9][10][11] (Fig. 1a). The C-N coupling of alkyl electrophiles, however, is largely under-developed (Fig. 1a). A perceived difficulty is β -hydrogen elimination from a metal alkyl intermediate originated from oxidative addition of the alkyl electrophile, which has posed considerable challenges in analogous C-C crosscoupling of alkyl electrophiles [12][13][14] . Moreover, the product-yielding C(sp 3 )-N reductive elimination step is rarely demonstrated 15 . A notable exception is the light-induced, copper-catalysed C-N coupling of alkyl halides recently developed [16][17][18] . Nevertheless, the scope of amine nucleophiles is limited to carbazoles 16,18 and amides 17,19 . Alternative, formal C-N coupling of alkyl electrophiles via the addition of alkyl radicals to nitroarenes has been reported 20,21 .The group of Baran has recently trailblazed the use of redox-active esters derived from alkyl carboxylic acids as superior surrogates of alkyl halides in decarboxylative C-C cross-coupling reactions [22][23][24] . Extension to a decarboxylative carbon-heteroatom, particularly C-B bond formation has also been reported 19,[25][26][27][28][29] . The key attributes of alkyl carboxylic acids 30,31 are their unparalleled availability, stability and non-toxic nature, which are in stark contrast with alkyl halides, ketones and aldehydes. While several precedents of decarboxylative imidation 32 and amination 19,33 are known, they are limited to a narrow scope of very special substrates or intramolecular reactions. A general metal-catalysed decarboxylative C-N coupling of redox-active esters with anilines will provide valuable methodology for the synthesis of alkylated anilines (Fig. 1b), which requires alkyl halides and carbonyl compounds 6 as starting reagents using the currently standard methods of alkylation and reductive amination, respectively. Further foreseen advantages of such a decarboxylative amination include applicability to bulky primary and secondary alkyl groups and immunity to over-alkylation, both of which are major limitations of direct alkylation (Fig. 1b). Despite its conceptual simplicity and resemblance to decarboxylative C-C coupling, the intermolecular decarboxylative C-N coupling of redoxactive esters poses significant hurdles. The activation principle of redox-active esters originates from amide-bond synthesis; thus, amide formation can compete when amine nucleophiles are used. Moreover, decarboxylative C-C coupling reactions of redox-active esters were, until now, all init...

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