Advances in indium-catalysed organic synthesis

Chauhan, Kamlesh K.; Frost, Christopher G.

doi:10.1039/a906657h

Cited by 201 publications

(29 citation statements)

References 26 publications

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“…At higher temperatures, high regioselectivities towards the isomerised isobornyl thio-functionalised structures 2 were obtained. The access to new compounds, the use of a catalytic amount of In(OTf) 3 under mild conditions, without the need for an additional ligand, and the potential to recover and recycle the catalyst [20] constitute further advantages of this new catalytic reaction.…”

Section: Discussionmentioning

confidence: 99%

Indium Triflate‐Catalysed Addition of Thio Compounds to Camphene: A Novel Route to 2,3,3‐Trimethyl‐2‐thiobicyclo[2.2.1]heptane Derivatives

et al. 2007

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Section: Discussionmentioning

confidence: 99%

Indium Triflate‐Catalysed Addition of Thio Compounds to Camphene: A Novel Route to 2,3,3‐Trimethyl‐2‐thiobicyclo[2.2.1]heptane Derivatives

et al. 2007

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“…Given the known acid sensitivity of simple alkyl-substituted furans we speculated that the purification of the furan product by chromatography on silica gel might be responsible for the moderate yields of the isolated products. [8] Accordingly, although the use of neutral alumina offered no advantage, purifications employing Florisil (magnesium silicate) or triethylamine-doped silica allowed the furan to be isolated in significantly increased yields (entries [8][9][10].…”

mentioning

confidence: 99%

“…For example, treatment of furan 3 g with acetic anhydride in the presence of catalytic In(OTf) 3 delivered the fully substituted heterocycle in 89 % yield (Scheme 5). [10] This overall process provides a concise and efficient route to fully substituted furans.…”

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confidence: 99%

An Alkyne Hydroacylation Route to Highly Substituted Furans

2011

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Heterocyclic compounds, such as the bioactive natural products pukalide and nakadomarin A, and the hugely successful drug molecules ranitidine (Zantac) and atorvastatin (Lipitor) are of great importance in pharmaceutical, agrochemical, and other fine-chemical applications (Scheme 1).[1] While there exists a range of methods for transforming relatively complex starting materials into substituted heterocycles, and for the functionalization of existing heterocycles, there is less precedent for methodology which involves the direct, regiodefined synthesis of highly substituted heterocycles from simple starting materials.[2] As such, new methods for the synthesis of substituted heterocycles (or their precursors) are potentially of significant value. This is particularly true if such methods do not suffer from the same drawbacks as the traditional syntheses of 1,4-dicarbonyl compounds, the classic substrates for the preparation of furans, thiophenes, and pyrroles; these syntheses are often either step-or atom-inefficient. The recent advances achieved in intermolecular alkene and alkyne hydroacylation chemistry means that these transformations are now ideal methods to exploit for the synthesis of heterocyclic molecules, because they employ simple substrates and commercially available catalyst systems, and generate no by-products because of their 100 % atom-economy. [3][4][5] In addition, a broad range of aldehydes can now be employed, and particularly in the case of alkyne hydroacylation, significant substitution of the unsaturated component can be tolerated, thus allowing for the regioselective production of highly substituted complex molecules in one catalytic intermolecular carbon-carbon bond forming step. Herein, we demonstrate the utility of intermolecular alkyne hydroacylation in the efficient synthesis of di-and trisubstituted furans and related heterocycles.g-Hydroxy-a,b-enones are known to undergo acid-catalyzed dehydrative cyclization to form furans, and this transformation has been exploited by several research groups, [6] most notably in the recent work from Donohoe et al. [7] The intermolecular hydroacylation of an aldehyde with readily available propargylic alcohols would permit the synthesis of g-hydroxy-a,b-enones with 100 % atom efficiency; coupling this carbon-carbon bond formation with an acid-catalyzed dehydrative cyclization would allow for the regioselective synthesis of di-or trisubstituted furans. The associated disconnection is novel for this type of heterocycle (Scheme 2).Our initial investigations to realize the above route to furans focused on the combination of propargyl alcohol 1 a and the S-chelating alkyl aldehyde 2 a (Table 1). The hydroacylative union of these two substrates using a dppe-derived Rh catalyst proceeded without incident. However, attempts to achieve a dehydrative cyclization using TFA provided only a small amount of the desired furan 3 a (entry 1). Reducing the time for the cyclization event to 1 hour, and then to 10 minutes, increased the yield of furan up to 50 % (entrie...

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“…For indium in particular, it is also worth noting that the unique behavior and redox properties of In I compounds (sometimes generated in situ) render such species useful as either reagents or catalysts used to effect several types of organic transformations; such reactions almost always proceed through the formation of organoindium intermediates or by-products [17][18][19][20][21][22][23][24]. In a similar vein, inorganic and organometallic In I reagents have been shown to insert into reactive carbon-element bonds to generate new In III species [2,3].…”

Section: Introductionmentioning

confidence: 99%