A [4 + 3] Annulation Reaction of aza-o-Quinone Methides with Arylcarbohydrazonoyl Chlorides for Synthesis of 2,3-Dihydro-1H-benzo[e][1,2,4]triazepines

Guo, Zhenyan; Jia, Hao; Liu, Honglei; Wang, Qijun; Huang, Jiaxing; Guo, Hongchao

doi:10.1021/acs.orglett.8b00990

Cited by 53 publications

(14 citation statements)

References 73 publications

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“…Guo also employed o-chloromethyl arylsulfonamides 2.11a in an unexpected two-step (4+3)-annulation with arylcarbohydrazonoyl chlorides 2.11b for the construction of 2,3-dihydro-1H-benzo[e][1,2,4]triazepines 2.11d (Scheme 2.11). 24 The reaction proceeded via the formation of the intermediate 2.11c, which could be isolated and was initially the major product before flash column chromatography purification triggered its conversion into 2.11d. This led to silica gel being added as the second step of the reaction to completely consume 2.11c.…”

Section: Special Topic Synthesismentioning

confidence: 99%

Recent Advances in Transition-Metal-Free (4+3)-Annulations

et al. 2021

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Abstract(4+3)-Annulations are incredibly versatile reactions which combine a 4-atom synthon and a 3-atom synthon to form both 7-membered carbocycles as well as heterocycles. We have previously reviewed transition-metal-catalyzed (4+3)-annulations. In this review, we will cover examples involving bases, NHCs, phosphines, Lewis and Brønsted acids as well as some rare examples of boronic acid catalysis and photocatalysis. In analogy to our previous review, we exclude annulations involving cyclic dienes like furan, pyrrole, cyclohexadiene or cyclopentadiene, as Chiu, Harmata, Fernándes and others have recently published reviews encompassing such substrates. We will however discuss the recent additions (2010–2020) to the literature on (4+3)-annulations involving other types of 4-atom-synthons.1 Introduction2 Bases3 Annulations Using N-Heterocyclic Carbenes3.1 N-Heterocyclic Carbenes (NHCs)3.2 N-Heterocyclic Carbenes and Base Dual-Activation4 Phosphines5 Acids5.1 Lewis Acids5.2 Brønsted Acids6 Boronic Acid Catalysis and Photocatalysis7 Conclusion

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Section: Special Topic Synthesismentioning

confidence: 99%

Recent Advances in Transition-Metal-Free (4+3)-Annulations

et al. 2021

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“…Analogously we expanded the (4+1)-cyclization methodology utilizing oxyphosphonium enolates for the construction of N-heterocyclic frameworks. Through the utilization of aza-ortho-quinone methides (aza-o-QM) 13 [26][27][28] as four-atom synthons, while employing Kukhtin-Ramirez conditions, we reported the construction of 2,3-dihydroindoles 14 (Scheme 5). 16 The assembly of 14 was accomplished utilizing 2-aminobenzyl chlorides 15, as aza-o-QM precursors, in the presence of two equivalents of -keto ester 1a and P(NMe 2 ) 3 providing the desired cycloadducts in yields ranging from 37-90% (Scheme 6a).…”

Section: Account Synlett 22 Aza-quinone Methides As Four-atom Synthons For the Assembly Of 23-dihydroindolesmentioning

confidence: 99%

(4+1)-Cycloadditions Exploiting the Biphilicity of Oxyphosphonium Enolates and RhII/PdII-Stabilized Metallocarbenes for the Construction of Five-Membered Frameworks

Tucker¹,

Ashfeld²

2021

Synlett

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Abstract(4+1)-Cyclizations are an underutilized disconnect for the formation of five-membered heterocyclic and carbocyclic frameworks. Herein we analyze methods employing oxyphosphonium enolates and RhII/PdII-metallocarbenes as C1 synthons in the presence of several four-atom components for the synthesis of 2,3-dihydrobenzofurans, 2,3-dihydroindoles, oxazolones, cyclopentenones, and pyrrolones.1 Introduction2 (4+1)-Cyclizations Employing Kukhtin–Ramirez-Like Reactivity3 (4+1)-Cyclizations Employing a Cyclopropanation/Ring-Expansion Sequence4 Pd-Catalyzed (4+1)-Cyclizations through Carbene Migratory Insertion/Reductive Elimination Processes5 Summary

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“…For example, nitrile imines were frequently employed in [3+2] coupling with alkenes to give various pyrazolines [13] . In addition, [3+3] [14] and [4+3] [15] cycloaddition reactions of nitrile imines were also developed to synthesize six‐ and seven‐membered nitrogen‐containing heterocycles. However, up to now, the cycloadditions of nitrile imines with alkenes to access pyrazoles directly (without any manipulation) has not been reported yet.…”

Section: Figurementioning

confidence: 99%

Synthesis of Pyrazoles through [3+2] Cyclization of Nitrile Imines with Cinnamaldehydes Followed by Air Oxidation

Gao¹,

Shi²,

Tian³

et al. 2021

ChemistrySelect

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An unprecedented [3+2] cycloaddition reaction of in situ generated nitrile imines with cinnamyl aldehydes followed by air oxidation has been successfully developed under mild conditions, providing an efficient approach to multisubstituted pyrazoles (up to 88 % yield). Preliminary mechanistic investigation implies that the final product is generated through oxidation in the presence of air. The prominent features of this reaction include mild conditions, simple operation and gram‐scale synthesis.

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A [4 + 3] Annulation Reaction of aza-o-Quinone Methides with Arylcarbohydrazonoyl Chlorides for Synthesis of 2,3-Dihydro-1H-benzo[e][1,2,4]triazepines

Cited by 53 publications

References 73 publications

Recent Advances in Transition-Metal-Free (4+3)-Annulations

Recent Advances in Transition-Metal-Free (4+3)-Annulations

(4+1)-Cycloadditions Exploiting the Biphilicity of Oxyphosphonium Enolates and RhII/PdII-Stabilized Metallocarbenes for the Construction of Five-Membered Frameworks

Synthesis of Pyrazoles through [3+2] Cyclization of Nitrile Imines with Cinnamaldehydes Followed by Air Oxidation

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