A new method for the cleavage of nitrobenzyl amides and ethers

Han, Seo‐Jung; Melo, Gabriel Fernando de; Stoltz, Brian M.

doi:10.1016/j.tetlet.2014.10.006

Cited by 9 publications

(9 citation statements)

References 23 publications

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“…In addition, the reaction system was efficient for the cleavage of allyl, prenyl, and cinnamyl protecting groups ( 1f – h ). To the best of our knowledge, almost no examples of removing both the electron-rich p -methoxybenzyl (PMB) group ( 1d ) and electron-deficient p -nitrobenzyl (PNB) group ( 1e ) by the same reaction conditions have been reported. Moreover, few reagents , are capable of simultaneously cleaving both benzyl and allyl groups.…”

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confidence: 99%

Pd-Catalyzed Debenzylation and Deallylation of Ethers and Esters with Sodium Hydride

Mao

Liu

et al. 2018

ACS Catal.

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Herein we demonstrate simply that the addition of Pd(OAc) 2 as a promotor switches the reactivity of a commonly used base NaH to a nucleophilic reductant. The reactivity is engineered into a palladium-catalyzed reductive debenzylation and deallylation of aryl ethers and esters. This operationally simple, mild protocol displays a broad substrate scope and a broad spectrum of functional group tolerance (>50 examples) and high chemoselectivity toward aryl ethers over aliphatic structures. Moreover, the dual reactivity of NaH as a base and a reductant is demonstrated in efficient synthetic elaboration.

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confidence: 99%

Pd-Catalyzed Debenzylation and Deallylation of Ethers and Esters with Sodium Hydride

Mao

Liu

et al. 2018

ACS Catal.

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“…However, the CH-activation reaction scope displayed by simplified model system 46 did not fully translate to the highly functionalized CH-activation precursors 48 and 52a/b , thus the attention was turned to the readily accessible enoate 53a/b and its elaboration to enone 61 and tertiary alcohol 63 . In this venture, conversion of the enoate appendage in 56 to the corresponding enone was realized through oxidative cleavage (OsO 4 , NaIO 4 ) and hydrolytic removal of the oxalamide and p -nitrobenzyl groups (LiOOH, then NaOH), followed by treatment of the resulting aldehyde ( 57 ) with alkynyl Grignard 59 and an Au-catalyzed Meyer-Schuster rearrangement of the alkynyl benzyl alcohol intermediate 58 . Alternatively, enone 61 could also be accessed via a Wittig reaction (with ylide 60 ) of the aforementioned aldehyde intermediate ( 57 ), but required more extensive chromatographic purifications to remove the ylide derived triphenylphosphoryl byproducts.…”

Section: Resultsmentioning

confidence: 99%

Organocatalytic and Late-Stage CH-Functionalization Enabled Asymmetric Synthesis of Communesin F and Putative Communesins

2017

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Herein we report the total syntheses of communesin F and putative members of the communesin family of polycyclic bis-aminal alkaloids. The successful strategy featured a novel organocatalytic reaction between two oxindole subunits to cast, after extensive optimization, the all-carbon vicinal quaternary stereocenters of the target molecule with high enantiocontrol. The resulting bis-oxindole intermediate further underwent a Ti(O Pr)-mediated dehydrative skeletal rearrangement to furnish the communesin core structure. Consider the ready availability and low-cost of unsubstituted isatin, and the inferior organocatalytic reaction employing a bromo-substituted substrate, a Pd(OAc)-catalyzed and oxalamide-directed aryl CH-alkenylation reaction was implemented to assemble the complete skeletal backbone of the target molecule. Collectively, the synthetic technologies disclosed herein constitute the first asymmetric organocatalytic approach to the communesins, together with a highly effective late-stage CH-functionalization in stark contrast to the bromoarene substrates employed in all of the past synthetic work.

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“… 36 Surprisingly, we discovered that removal of the o -nitrobenzyl group to produce compound 53 was also accomplished using 20% aq NaOH in methanol at 75 °C in 70% yield—a previously unknown deprotection protocol. 37 Aminal 53 has been advanced by the Qin group to communesin F, 5g thus completing our formal synthesis of the natural product.…”

Section: Results and Discussionmentioning

confidence: 99%

Evolution of a Unified, Stereodivergent Approach to the Synthesis of Communesin F and Perophoramidine

et al. 2014

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Expedient synthetic approaches to the highly functionalized polycyclic alkaloids communesin F and perophoramidine are described using a unified approach featuring a key decarboxylative allylic alkylation to access a crucial and highly congested 3,3-disubstituted oxindole. Described are two distinct, stereoselective alkylations that produce structures in divergent diastereomeric series possessing the critical vicinal all-carbon quaternary centers needed for each synthesis. Synthetic studies toward these challenging core structures have revealed a number of unanticipated modes of reactivity inherent to these complex alkaloid scaffolds. Additionally, several novel and interesting intermediates en route to the target natural products, such as an intriguing propellane hexacyclic oxindole encountered in the communesin F sequence, are disclosed. Indeed, such unanticipated structures may prove to be convenient strategic intermediates in future syntheses.

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A new method for the cleavage of nitrobenzyl amides and ethers

Cited by 9 publications

References 23 publications

Pd-Catalyzed Debenzylation and Deallylation of Ethers and Esters with Sodium Hydride

Pd-Catalyzed Debenzylation and Deallylation of Ethers and Esters with Sodium Hydride

Organocatalytic and Late-Stage CH-Functionalization Enabled Asymmetric Synthesis of Communesin F and Putative Communesins

Evolution of a Unified, Stereodivergent Approach to the Synthesis of Communesin F and Perophoramidine

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