KO<i>t</i>Bu‐Mediated Domino Isomerization and Functionalization of Aromatic Allylic Alcohols

Suchand, Basuli; Satyanarayana, Gedu

doi:10.1002/ejoc.201700440

Cited by 24 publications

(13 citation statements)

References 63 publications

(9 reference statements)

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“…The reaction can be initiated by hydrogen‐atom transfer (HAT) from PhCH 2 O − to phenylacetylene to form radicals A and A′ . The transfer of a hydrogen radical from the benzylic position of the corresponding alkoxides has previously been proposed . The transfer of a hydrogen radical to phenylacetylene was also documented before .…”

Section: Methodsmentioning

confidence: 75%

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KO^tBu: Unusual Regioselectivity through a Radical Mechanism

et al. 2019

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We report aC À Cb ond-forming reaction between benzyl alcohols and alkynes in the presence of ac atalytic amount of KO t Bu to form a-alkylated ketones in which the C = Og roup is located on the side derived from the alcohol. The reaction proceeds under thermal conditions (125 8 8C) and produces no waste,m aking the reaction highly atom efficient, environmentally benign, and sustainable.B ased on our mechanistic investigations,w ep ropose that the reaction proceeds through radical pathways.

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Section: Methodsmentioning

confidence: 75%

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KO^tBu: Unusual Regioselectivity through a Radical Mechanism

et al. 2019

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“…Firstly, one‐pot process could generate the diols via Heck reaction and reduction of the resultant ketones with sodium borohydride, while, in the second pot diol would undergo Lewis acid induced intramolecular C−O bond formation to furnish the flavans. Since, our group extensively focused on the use of allylic alcohols and their application by means of coupling . The synthetic study was initiated by choosing allylic alcohol 5a and 2‐iodophenol 6a as the model substrates, and the results are as summarized in Table .…”

Section: Resultsmentioning

confidence: 99%

One‐Pot Heck and Reduction: Application towards Efficient Synthesis of Flavans Promoted by Lewis Acid

et al. 2017

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“…In the subsequent reaction step the hydride center is transferred from the metal center to the carbonyl C atom of D ( XIII ) and then one of the H 2 molecules generated earlier in the reaction takes part in the first re‐hydrogenation step ( XIV ) leading the reaction to XV . After dissociation of the unsaturated alcohol E from XV the active species is regenerated ( I’’’ ) while E isomerizes base catalyzed to ketone F , which associates to I’’’ and forms XVI . It should be noted that in principle the olefinic C−C‐double bond of E could also be hydrogenated.…”

Section: Methodsmentioning

confidence: 99%

On the Mechanism of the Ruthenium‐catalyzed β‐methylation of Alcohols with Methanol

et al. 2020

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Selective β-methylation of alcohols with methanol has been recently described using a catalytic system comprising the ruthenium pincer complex [RuH(CO)(BH 4 )(HN(C 2 H 4 PPh 2 ) 2 )]-(Ru-MACHO-BH) 1 and alcoholate bases as co-catalysts. [1] Here we present a detailed mechanistic analysis for the mono-methylation of 1-phenyl-propane-1-ol 2 a as prototypical example. Several experimentally observed intermediates were localized as stable minima on the DFT-derived energy surface of the entire reaction network. The ruthenium complex [Ru(H) 2 (CO) (HN(C 2 H 4 PPh 2 ) 2 )] I was inferred as the active species catalyzing the de-hydrogenation/re-hydrogenation of substrates and intermediates ("hydrogen borrowing"). The hydrogen-bonded alcohol adduct of this complex was identified as the lowest lying intermediate (TDI). The CÀ C bond formation results from a base-catalyzed aldol reaction comprising the transition state with the highest energy (TDTS). Experimentally determined Gibbs free activation barriers of 26.1 kcal/mol and 26.0 kcal/mol in methanol and toluene as solvents, respectively, are reflected well by the computed energy span of the complex reaction network (29.2 kcal/mol).Catalytic methods for the introduction of methyl groups into organic substrates using methanol as C1 building block offer attractive synthetic pathways in line with the principles of Green Chemistry. In particular the synthesis of methyl branches in aliphatic carbon chains using methanol remains a significant challenge, however. [2] Most recently we showed that ruthenium pincer complex [RuH(CO)(BH 4 )(HN(C 2 H 4 PPh 2 ) 2 )]-(Ru-MACHO-BH) 1 is a versatile pre-catalyst for this reaction. [1] For a broad range of primary and secondary alcohols as substrates, the methyl group is introduced selectively in βposition providing the branched products in good to very high yields with water as the only byproduct (Scheme 1). The synthetic methodology has been transferred and largely extended by the use of Mn(I)-MACHO complex most recently. [3] In this work we present a mechanistic analysis of this transformation with the original ruthenium catalyst based on experimentally and theoretically compiled data.From the results of the synthetic studies, we postulated a working hypothesis for the catalytic process exemplified in Scheme 2 for the mono-methylation of 1-phenyl-propane-1-ol 2 a to 1-phenyl-2-methyl-propane-1-ol 3 a. The overall trans-formation involves five individual cycles A-E forming a complex reaction network. Initially both alcohol and methanol are dehydrogenated by the transition metal catalyst to form ketone and formaldehyde, respectively. [4] Subsequently, a base-catalyzed aldol condensation generates the CÀ C bond [5] and finally the unsaturated intermediate is step-wise re-hydrogenated at the ruthenium catalyst.The involvement of the de-and re-hydrogenation cycles is corroborated with a series of control experiments summarized in scheme 3. 1-phenyl-propane-1-ol 2 a reacts with 13 CH 3 OH to the mono-methylated product containing the 13 ...

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KOtBu‐Mediated Domino Isomerization and Functionalization of Aromatic Allylic Alcohols

Cited by 24 publications

References 63 publications

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KO^tBu: Unusual Regioselectivity through a Radical Mechanism

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KO^tBu: Unusual Regioselectivity through a Radical Mechanism

One‐Pot Heck and Reduction: Application towards Efficient Synthesis of Flavans Promoted by Lewis Acid

On the Mechanism of the Ruthenium‐catalyzed β‐methylation of Alcohols with Methanol

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KOtBu‐Mediated Domino Isomerization and Functionalization of Aromatic Allylic Alcohols

Cited by 24 publications

References 63 publications

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KOtBu: Unusual Regioselectivity through a Radical Mechanism

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KOtBu: Unusual Regioselectivity through a Radical Mechanism

One‐Pot Heck and Reduction: Application towards Efficient Synthesis of Flavans Promoted by Lewis Acid

On the Mechanism of the Ruthenium‐catalyzed β‐methylation of Alcohols with Methanol

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C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KO^tBu: Unusual Regioselectivity through a Radical Mechanism

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KO^tBu: Unusual Regioselectivity through a Radical Mechanism