1-Methyl-1-azacyclohexa-2,3-diene(N−B)borane − Generation and Interception of an Unsymmetrical Isodihydropyridine

Drinkuth, Stefan; Groetsch, Stefan; Peters, E.‐M.; Peters, Karl; Christl, Manfred

doi:10.1002/1099-0690(200107)2001:14<2665::aid-ejoc2665>3.0.co;2-i

Cited by 23 publications

(9 citation statements)

References 26 publications

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“…164 An unsymmetrical isodihydropyridine (an 1azacyclohexa-2,3-diene prepared by base-induced dehydrohalogenation of a 3-bromo-1,2,5,6-tetrahydropyridine) was efficiently trapped by [4 ϩ 2] and [2 ϩ 2] cycloadditions with furan and styrene, respectively. 165 The photocycloaddition of cyanoethylenes onto 1,4-dihydropyridines has been reported. Photoirradiation of N-alkoxycarbonyl-1,2-dihydropyridines 105 promoted the concerted electrocyclization to yield the 2-azabicyclo[2.2.0]hexene system 106, which was, afterwards, successfully transformed into a variety of rearranged and nonrearranged skeletal types 107-109 (Scheme 29).…”

Section: Pericyclic Reactionsmentioning

confidence: 99%

Recent developments in the chemistry of dihydropyridines

Lavilla

2002

J. Chem. Soc., Perkin Trans. 1

367

162

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Section: Pericyclic Reactionsmentioning

confidence: 99%

Recent developments in the chemistry of dihydropyridines

Lavilla

2002

J. Chem. Soc., Perkin Trans. 1

367

162

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“…A diverse range of stereochemically‐rich products can be accessed via highly endo selective Diels–Alder cycloadditions to strained cyclic allenes, as shown by cycloadducts 1 – 4 (Figure 1 a). [2b–e] Our groups [2c,d,f–i] and others [2j,k] have generated strained cyclic allenes from silyl triflates, 5 , and have found that in situ generated heterocyclic allenes, such as unsubstituted allenes 7 and 8 , participate in highly endo selective Diels–Alder reactions to provide adducts 13 – 22 (Figure 1 b). [2c,d] …”

Section: Introductionmentioning

confidence: 99%

Origins of Endo Selectivity in Diels–Alder Reactions of Cyclic Allene Dienophiles

et al. 2021

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Strained cyclic allenes, first discovered in 1966 by Wittig and co‐workers, have recently emerged as valuable synthetic building blocks. Previous experimental investigations, and computations reported here, demonstrate that the Diels–Alder reactions of furans and pyrroles with 1,2‐cyclohexadiene and oxa‐ and azaheterocyclic analogs proceed with endo selectivity. This endo selectivity gives the adduct with the allylic saturated carbon of the cyclic allene endo to the diene carbons. The selectivity is very general and useful in synthetic applications. Our computational study establishes the origins of this endo selectivity. We analyze the helical frontier molecular orbitals of strained cyclic allenes and show how secondary orbital and electrostatic effects influence stereoselectivity. The LUMO of carbon‐3 of the allene (C‐3 is not involved in primary orbital interactions) interacts in a stabilizing fashion with the HOMO of the diene in such a way that the carbon of the cyclic allene attached to C‐1 favors the endo position in the transition state. The furan LUMO, allene HOMO interaction reinforces this preference. These mechanistic studies are expected to prompt the further use of long‐avoided strained cyclic allenes in chemical synthesis.

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“…More recently, efforts were focused on the isomeric 1-aza-2,3-cyclohexadiene. Although this was found to be unstable, N -borylation permitted access to azacyclic allene 8 26 . Additional discoveries in this field include the synthesis of a cephalosporinderived cyclic allene formation by Elliott and co-workers 27–29 and several studies pertaining to heterocyclic isoarenes 7,30–36 .…”

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confidence: 99%

Diels–Alder cycloadditions of strained azacyclic allenes

et al. 2018

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For over a century, the structures and reactivities of strained organic compounds have captivated the chemical community. Whereas triple-bond-containing strained intermediates have been well studied, cyclic allenes have received far less attention. Additionally, studies of cyclic allenes that bear heteroatoms in the ring are scarce. We report an experimental and computational study of azacyclic allenes, which features syntheses of stable allene precursors, the mild generation and Diels-Alder trapping of the desired cyclic allenes, and explanations of the observed regio- and diastereoselectivities. Furthermore, we show that stereochemical information can be transferred from an enantioenriched silyl triflate starting material to a Diels-Alder cycloadduct by way of a stereochemically defined azacyclic allene intermediate. These studies demonstrate that heteroatom-containing cyclic allenes, despite previously being overlooked as valuable synthetic intermediates, may be harnessed for the construction of complex molecular scaffolds bearing multiple stereogenic centres.

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1-Methyl-1-azacyclohexa-2,3-diene(N−B)borane − Generation and Interception of an Unsymmetrical Isodihydropyridine

Cited by 23 publications

References 26 publications

Recent developments in the chemistry of dihydropyridines

Recent developments in the chemistry of dihydropyridines

Origins of Endo Selectivity in Diels–Alder Reactions of Cyclic Allene Dienophiles

Diels–Alder cycloadditions of strained azacyclic allenes

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