Copper-catalyzed tandem alkynylation, propargyl–allenyl isomerization, 6π-electrocyclization of Morita–Baylis–Hillman adducts to naphthalenes

Lim, Jin Woo; Kim, Ko Hoon; Kim, Se Hee; Kim, Jae Nyoung

doi:10.1016/j.tetlet.2012.07.126

Cited by 41 publications

(10 citation statements)

References 49 publications

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“…The ylide carbon atom of 3a could abstract the amide proton and a following elimination of triphenylphosphine oxide would generate II ( vide infra ). Then, the ketenimine could be transformed to aminonaphthalene 4a via 6π‐electrocyclic ring closure (ERC) process …”

Section: Methodsmentioning

confidence: 99%

Synthesis of Aminonaphthalenes from Morita–Baylis–Hillman Carbonates via 6π‐Electrocyclization of Ketenimine Intermediates

Min

Roh

Ryu

et al. 2016

Bulletin Korean Chem Soc

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Morita-Baylis-Hillman (MBH) adducts have been used extensively for the synthesis of various cyclic and acyclic compounds. 1 One of the important chemical transformations of MBH adducts starts from a conversion of electrophilic β-carbon of acrylate moiety to a nucleophilic center by forming MBH adduct-derived phosphorous ylide I, as shown in Scheme 1. 2,3 The MBH ylide I could be formed by the reaction of MBH bromide or acetate with tertiary phosphine in the presence of base, 2 and the ylide has been used for the synthesis of Ramirez ylides, 2a spirooxindoles, 2b,c poly-substituted aromatics, 2e-h and 1,3dienes. 2i-k The ylide I could also be generated more efficiently from MBH carbonate 1a and tertiary phosphine without an external base, 3 and the ylide has been used extensively for the synthesis of thiophenes, 3a pyrazoles, 3b isoquinolines, 3c butenolides, 3e and spirooxindoles. 3o Very recently, we reported a stereoselective synthetic method of 3,4-dibenzylidenepyrrolidine-2,5-diones by the reaction of ylide I and phenyl isocyanate (2a) to form carbamoyl stabilized ylide 3a, and a following Wittig reaction with benzaldehyde (Scheme 1). 4 The amide proton of 3a was eliminated during the acid-catalyzed cyclization as MeOH. As a continuous work, we envisioned that ylide 3a could be converted to ketenimine intermediate II by liberation of triphenylphosphine oxide in the absence of an acid catalyst at elevated temperature. The ylide carbon atom of 3a could abstract the amide proton and a following elimination of triphenylphosphine oxide would generate II (vide infra). Then, the ketenimine could be transformed to aminonaphthalene 4a 5 via 6π-electrocyclic ring closure (ERC) process. [6][7][8] In order to check the feasibility of our assumption, a toluene solution of 3a 4 was heated to reflux for 3 h. To our delight, methyl 4-phenylaminonaphthalene-2-carboxylate (4a) was obtained in good yield (72%). When we used benzene as a solvent, a long reaction time (20 h) was required and the yield was moderate (51%). In addition, 4a could be synthesized directly from MBH carbonate 1a in one-pot procedure in good yield (63%) by the reaction of 1a and PPh 3 (1.1 equiv) in toluene at room temperature (5 min) to form I, addition of phenyl isocyanate (2a, 1.1 equiv) to form 3a (80 C, 1 h), and a final heating to reflux of the reaction mixture (3 h). 9 The yield of one-pot reaction (63%) was better than the two-pot procedure (68/72% = 49%). The structure of 4a was confirmed unequivocally by its crystal structure, and the structure of 4a is shown in Scheme 1 along with the crystal structure of 3a. 4,10 Encouraged by the successful result various MBH carbonates 1b-1h were prepared, 3,4 and the reactions with some representative isocyanates 2a-2d have been carried out in one-pot manner. The results are summarized in Table 1. The reactions of 1b and 1c afforded 4b (52%) and 4c (54%) in moderate yields. The reaction of 4-nitrophenyl derivative 1d afforded 4d in somewhat lower yield (44%). The reactions of 1e-1g afforded 4e-4g in moder...

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Section: Methodsmentioning

confidence: 99%

Synthesis of Aminonaphthalenes from Morita–Baylis–Hillman Carbonates via 6π‐Electrocyclization of Ketenimine Intermediates

Min

Roh

Ryu

et al. 2016

Bulletin Korean Chem Soc

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“…We also observed that an intramolecular Friedel‐Crafts (IMFC) alkenylation of the pyrazole 2a could produce benzocyclohepta[1,2‐ c ]pyrazole 3a in the presence of H 2 SO 4 via the vinyl cation intermediate I . The pyrazole 2a , bearing an arylpropargyl moiety at position 4, was prepared from Morita–Baylis–Hillman (MBH) adduct by sequential bromination, introduction of arylpropargyl moiety to form α,β‐enone 1a , and a one‐pot synthesis of pyrazole 2a by the reaction of 1a and phenylhydrazine …”

Section: Methodsmentioning

confidence: 98%

“…The formation of a trace amount of regioisomer was observed; however, it could not be isolated in appreciable amount. The selective alkenylation at position 1 of the naphthalene ring of 2g is due to a small loss of the resonance energy of the naphthalene during the Friedel‐Crafts reaction 1,3a,7e . The reaction of 3‐ethylpyrazole derivative 2h gave 3h in a reasonable yield (56%).…”

Section: Methodsmentioning

confidence: 99%

Facile Synthesis of Benzocyclohepta[1,2‐c]pyrazoles Starting from Morita–Baylis–Hillman Adducts Via an Intramolecular Friedel‐Crafts Alkenylation

Lee

Moon

et al. 2015

Bulletin Korean Chem Soc

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“…Of interest are also cyclizations of aromatic enynes and enediynes,12 couplings of alkynes and aromatic carbonyl compounds,13 the ring‐closing metathesis,14 the ring enlargement of strained rings,15 and the Dötz reaction 16. However, the number of approaches based on Cu(I)‐catalyzed reactions is only limited 4a–d…”

Section: Introductionmentioning

confidence: 99%

Synergy between Palladium and Potassium Species for Efficient Activation of Carbon Monoxide in the Synthesis of Dimethyl Carbonate

et al. 2015

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Copper-catalyzed tandem alkynylation, propargyl–allenyl isomerization, 6π-electrocyclization of Morita–Baylis–Hillman adducts to naphthalenes

Cited by 41 publications

References 49 publications

Synthesis of Aminonaphthalenes from Morita–Baylis–Hillman Carbonates via 6π‐Electrocyclization of Ketenimine Intermediates

Synthesis of Aminonaphthalenes from Morita–Baylis–Hillman Carbonates via 6π‐Electrocyclization of Ketenimine Intermediates

Facile Synthesis of Benzocyclohepta[1,2‐c]pyrazoles Starting from Morita–Baylis–Hillman Adducts Via an Intramolecular Friedel‐Crafts Alkenylation

Synergy between Palladium and Potassium Species for Efficient Activation of Carbon Monoxide in the Synthesis of Dimethyl Carbonate

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