Diels-Alder Reactions of Phenyl-Substituted 2-Pyrones: Direction of Addition with Phenylacetylene

Kohl, Robert; Katto, T.; Braham, J. N.; Stille, J. K.

doi:10.1021/ma60062a011

Cited by 11 publications

(3 citation statements)

References 6 publications

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“…The other products 8 and 9 were unexpected, resulting from a noteworthy Diels–Alder reaction (DAR) of 3 with the 2‐pyridine ring, followed by ring fragmentation (single‐crystal X‐ray structures of 8 and 9 confirmed the molecular connectivity, correlating with NMR spectroscopy, see the Supporting Information). Compound 9 shows that the 2‐pyrone participated in a secondary inverse electron demand DAR . Along with 6 g , both 8 and 9 derive from 4 g , where the DARs and 2‐pyridyl fragmentation are secondary reactions.…”

Section: Methodsmentioning

confidence: 99%

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

et al. 2016

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Manganese‐catalyzed C−H bond activation chemistry is emerging as a powerful and complementary method for molecular functionalization. A highly reactive seven‐membered MnI intermediate is detected and characterized that is effective for H‐transfer or reductive elimination to deliver alkenylated or pyridinium products, respectively. The two pathways are determined at MnI by judicious choice of an electron‐deficient 2‐pyrone substrate containing a 2‐pyridyl directing group, which undergoes regioselective C−H bond activation, serving as a valuable system for probing the mechanistic features of Mn C−H bond activation chemistry.

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Section: Methodsmentioning

confidence: 99%

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

et al. 2016

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“…Compound 9 shows that the 2-pyrone participated in as econdary inverse electron demand DAR. [14] Along with 6g,b oth 8 and 9 derive from 4g,w here the DARs and 2-pyridyl fragmentation are secondary reactions.…”

Section: Angewandte Chemiementioning

confidence: 99%

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

et al. 2016

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Manganese-catalyzed C À Hbond activation chemistry is emerging as ap owerful and complementary method for molecular functionalization. Ah ighly reactive seven-membered Mn I intermediate is detected and characterized that is effective for H-transfer or reductive elimination to deliver alkenylated or pyridinium products,r espectively.T he two pathwaysa re determined at Mn I by judicious choice of an electron-deficient 2-pyrone substrate containing a2 -pyridyl directing group,w hichu ndergoes regioselective C À Hb ond activation, serving as av aluable system for probing the mechanistic features of Mn CÀHb ond activation chemistry.C À Hb ond activation-functionalization chemistry is ac entral arena for catalyst development and synthetic application.[1] Tr ansition metals mediate the efficient and selective activation of CÀHb onds,w ith recent attention focusing on environmentally benign and sustainable metals,f or example, Mn, Co,F e, and Cu.[2] Mn I promotes CÀHa ctivation of substrates containing nitrogen-directing groups.[3] Fore xample, 1 gives cyclomanganated complex 2,w ith subsequent reaction with alkyne 3 forming aproposed 7-membered ring intermediate 4 (Scheme 1).[4] Formation of either 5, 6,o r7 results from reductive elimination, H-transfer,o rd ehydrogenative annulation, respectively.Processes utilizing Mn I ,p articularly [Mn(C^N)(CO) 4 ] 2, [5, 6] have been of broad interest. Them echanistic features of the remarkable synthetic work of Ackermann and Wang, [3,4] where intermediates 4a-c have been proposed, prompted us to examine whether they could be detected and characterized and then subsequently be shown to deliver organic products such as 5-7.C omplexes 4d-f,f ormed by insertion of internal alkynes are known, [6,7] but their competence in terms of af ully connected reaction system, affording organic products,h as not been examined. As 18-electron species containing four CO ligands,p ossessing high thermodynamic stability,t hey are unlikely to be directly involved in the catalytic cycle.[8]Herein we describe asuitable reaction system (1g!4g! 5g or 6g,S cheme 1) that takes advantage of the exquisite reactivity of an electron-deficient 2-pyrone ring system containing a2 -pyridyl directing group (1g). We recognized that the 2-pyrone could act as ah emilabile ligand in 7-membered manganacycle 4g,p otentially providing sufficient stabilisation for observation of this key intermediate.O ur findings demonstrate that 4g acts as ac entral manifold to reductive elimination and H-transfer, giving products 5g and 6g,respectively,w ith details described herein.Our study began with the reaction of 2-pyrone 1g with BnMn(CO) 5 in hexane at 75 8 8C, which gave cyclometalated 2g cleanly and in quantitative yield (Scheme 2). Complex 2g was fully characterized (see the Supporting Information);asingle crystal X-ray structure confirmed that regioselective CÀH activation occurred at C3, in keeping with Pd II -direct arylations of 2-pyrones, [9] albeit most likely by a s-CAM-type process. [10] We hypothesized tha...

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“…20,21 Intramolecular DA reaction on pyrones has a potential to generate complex systems. 22,23 The DA reaction of 2-pyrones has been employed in the synthesis of many natural products and related compounds, [24][25][26] like quinones, 14,15 benzenoids, 27,28 and complex bicyclo compounds. 29 The diene behavior of 2-pyrones can be modified by introducing appropriate substituents on the ring.…”

mentioning

confidence: 99%

Facile, Diversity-Oriented, Normal-Electron-Demand Diels–Alder Reactions of 6-Amino-2H-pyran-2-ones with Diethyl Acetylenedicarboxylate, 1,4-Naphthoquinone, and N-Phenylmaleimide

Khatri

Samant

2014

Synthesis

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A series of 6-amino-4-methoxyphenyl-2H-pyran-2-ones, having an electron-rich diene system, capable of undergoing normalelectron-demand (NED) Diels-Alder reaction, were synthesized. The Diels-Alder reaction of these pyrones with electron-deficient dienophiles-diethyl acetylene dicarboxylate, 1,4-naphthoquinone, and Nphenylmaleimide-followed three different pathways and gave structurally diverse products, aminobenzenes, aminoanthraquinones, and aminopolycyclic diimides, respectively. The amino group at the 6-position activated substantially the pyrone ring towards NED Diels-Alder reaction and the reaction has a potential to generate great structural diversity.

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Diels-Alder Reactions of Phenyl-Substituted 2-Pyrones: Direction of Addition with Phenylacetylene

Cited by 11 publications

References 6 publications

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

Facile, Diversity-Oriented, Normal-Electron-Demand Diels–Alder Reactions of 6-Amino-2H-pyran-2-ones with Diethyl Acetylenedicarboxylate, 1,4-Naphthoquinone, and N-Phenylmaleimide

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Diels-Alder Reactions of Phenyl-Substituted 2-Pyrones: Direction of Addition with Phenylacetylene

Cited by 11 publications

References 6 publications

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

Facile, Diversity-Oriented, Normal-Electron-Demand Diels–Alder Reactions of 6-Amino-2H-pyran-2-ones with Diethyl Acetylene­dicarboxylate, 1,4-Naphthoquinone, and N-Phenylmaleimide

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Facile, Diversity-Oriented, Normal-Electron-Demand Diels–Alder Reactions of 6-Amino-2H-pyran-2-ones with Diethyl Acetylenedicarboxylate, 1,4-Naphthoquinone, and N-Phenylmaleimide