The [1,4]oxazino[4,3-a]azepine ring system: Construction from morpholinoallenes and a structural study

Maas, Gerhard; Manz, Berthold; Mayer, Theo; Werz, Udo

doi:10.1016/s0040-4020(98)01132-6

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…It should be noted that a -annulated benzazepine derivatives 5 and 7 have two stereogenic centers but only one diastereomer was obtained. The trans configuration was derived from the similarity of the relevant 1 H NMR data with those of closely related systems the structure of which was established by X-ray structure determination. 11a,, This configuration is in agreement with a conrotatory 8π electrocyclization mode of azomethine ylide intermediates 1 (Scheme ) followed by a suprafacial [1,5]-H shift.…”

Section: Resultsmentioning

confidence: 87%

Synthesis of Pyrroles from 1-Dialkylamino-3-phosphoryl(or phosphanyl)allenes through 1,5-Cyclization of Conjugated Azomethine Ylide Intermediates

Reisser

Maas

2004

J. Org. Chem.

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1-Dialkylamino-1,3-diaryl-3-diphenylphosphanylallenes 3a-e are thermally converted into a-annulated 3,5-diarylpyrroles 6a-f and [a]-annulated benzo[c]azepines 7a,b,d. These transformations are likely to include conjugated azomethine ylide intermediates that can undergo either a 1,5- or a 1,7-electrocyclization. The periselectivity is markedly shifted toward 1,5-cyclization when the diphenylphosphanyl substituent is replaced by the diphenylphosphoryl group. Thus, 1-dialkylamino-3-(diphenylphosphoryl)allenes 4a-f yield pyrroles 6 exclusively and with improved yields, unless the 3-aryl substituent in the allene is too electron-rich (e.g., benzodioxol-5-yl, 4f --> 7f). The preparation and thermal transformation of aminoallenes 4 over three or four steps can be conducted as a one-pot procedure, thus providing a convenient synthesis of [a]-annulated 3,5-diarylpyrroles from enaminoketones.

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Section: Resultsmentioning

confidence: 87%

Synthesis of Pyrroles from 1-Dialkylamino-3-phosphoryl(or phosphanyl)allenes through 1,5-Cyclization of Conjugated Azomethine Ylide Intermediates

Reisser

Maas

2004

J. Org. Chem.

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“…The chemistry of the novel electron‐rich (3‐morpholinoallenyl)phosphanes 4 and 5 would be expected to be dominated by transformations of the two reactive functionalities: the enamine moiety16 and the (allenyl)phosphane unit 17. This was confirmed by some transformations carried out with allene 4 (Scheme ).…”

Section: Resultsmentioning

confidence: 89%

Propyne Iminium Salts and Phosphorus(III) Nucleophiles: Synthesis of (3‐Morpholinoallenyl)phosphanes and ‐phosphane Oxides or 1‐(Morpholinopropargyl)phosphanes and ‐phosphonates

2003

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Treatment of 4‐(1,3‐diphenyl‐l‐propynylidene)morpholinium triflate (1a) with the neutral phosphorus nucleophiles Me3Si−PPh2, Me3Si−P(Ph)C5H11, and Me3SiO−PPh2 affords (3‐morpholinoallenyl)phosphanes 4 and 5 and (3‐morpholinoallenyl)phosphane oxide 11, respectively. In contrast to these conjugate addition reactions at the ambident propyne iminium moiety of 1a, nucleophilic attack by Me3Si−PEt2 and Me3SiO−P(OEt)2 takes place at the iminium function and gives (1‐morpholinopropargyl)phosphane 6 and (1‐morpholinopropargyl)phosphonate 12, respectively. Propyne iminium salt 1b reacts with Me3Si−PPh2 to form (3‐morpholino‐1,3‐butadienyl)phosphane oxide 8. The bis(donor)‐substituted allene 4 is transformed by oxidation of the phosphorus substituent into the push‐pull substituted allenylphosphane oxide 11. Treatment of allene 4 with elemental sulfur results in the formation of betaine 16, which undergoes [3+2] cycloaddition reactions with acetylenic esters to afford 5‐benzylidene‐4,5‐dihydrothiophenes 17 and 18. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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“…24 Following this concept, Mass et al synthesized azepine derivatives by treating morpholinoallenes (6a) with electron-deficient alkynes (2b) (Scheme 6A). 29 At first, internal C�C bond-selective [2 + 2] cycloaddition occurs at room temperature, furnishing the major cycloadduct (E)-6b, which readily undergoes thermal rearrangement to the ring-expanded oxazinoazepine 6c. Considering the reactivity patterns, known as "tert-amino effect" and "α-cyclization of tertiary amine", the authors proposed two sequences of events: H migration and 8πelectrocyclization for ring expansion.…”

Section: Historical Background Of Intermolecular Aa Couplingmentioning

confidence: 99%

“…As aforementioned, utilization of electron-rich allenes in cycloaddition with alkynes has been established since the studies of Brandsma . Following this concept, Mass et al synthesized azepine derivatives by treating morpholinoallenes ( 6a ) with electron-deficient alkynes ( 2b ) (Scheme A) . At first, internal CC bond-selective [2 + 2] cycloaddition occurs at room temperature, furnishing the major cycloadduct ( E )- 6b , which readily undergoes thermal rearrangement to the ring-expanded oxazinoazepine 6c .…”

Section: Historical Background Of Intermolecular Aa Couplingmentioning

confidence: 99%

Intermolecular Allene–Alkyne Coupling: A Significantly Useful Synthetic Transformation

Pradhan,

Park

2024

ACS Catal.

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Because of its wide applicability in the synthesis of diverse unsaturated building blocks, allene−alkyne (AA) coupling has emerged as a powerful methodology to drive useful chemical transformations in the past two decades. Considering recent discoveries in this active research area, in this Review, we aim to support chemists in the selection of suitable methods, particularly intermolecular approaches, according to the synthesis needs. However, inherent similarities between the reactivities of π-systems create considerable obstacles while predicting selectivity in an intermolecular platform. Therefore, herein, intermolecular couplings for the chemoselective, stereoselective, and regioselective syntheses of acyclic and cyclic C-skeletons are reviewed. However, considering the lack of a well-organized review in this field, we initially provide a brief historical overview of the types of thermally induced reactions that are mostly feasible for electronically biased coupling components and are nonselective. Subsequently, emerging selective strategies are described, which include activator-controlled and neighboring functional group-assisted regio-, stereo-, and π-skeleton-divergent processes. Overall, this Review is divided into two parts. In the first part, strategies for the fabrication of acyclic C-skeletons are explained according to the reaction types. In the second part, synthetic transformations affording cyclic structures are reviewed based on the substrate class (that is, nonassisted and assisted substrates). Key reaction intermediates of each subset of coupling and factors affecting productselective discrimination of the active species with the highlight of rationale are systemically summarized. Understanding of these substrate structure-and catalyst-dependent factors provides insights into the regulation of the chemoselectivities of title AA crosscouplings and, therefore, the design of alternative catalytic routes with distinct mechanistic features.

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The [1,4]oxazino[4,3-a]azepine ring system: Construction from morpholinoallenes and a structural study

Cited by 9 publications

References 14 publications

Synthesis of Pyrroles from 1-Dialkylamino-3-phosphoryl(or phosphanyl)allenes through 1,5-Cyclization of Conjugated Azomethine Ylide Intermediates

Synthesis of Pyrroles from 1-Dialkylamino-3-phosphoryl(or phosphanyl)allenes through 1,5-Cyclization of Conjugated Azomethine Ylide Intermediates

Propyne Iminium Salts and Phosphorus(III) Nucleophiles: Synthesis of (3‐Morpholinoallenyl)phosphanes and ‐phosphane Oxides or 1‐(Morpholinopropargyl)phosphanes and ‐phosphonates

Intermolecular Allene–Alkyne Coupling: A Significantly Useful Synthetic Transformation

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