Hydrazides as Tunable Reagents for Alkene Hydroamination and Aminocarbonylation

Abstract

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5-(Methylthio)tetrazoles as versatile synthons in the stereoselective synthesis of polycyclic pyrazolines via photoinduced intramolecular nitrile imine–alkene 1,3-dipolar cycloaddition

“…The thioimidate moiety could also be hydrolyzed efficiently to the cyclic hydrazide 17 . Such pyrazolidinones can undergo N – N -bond cleavage to prepare β-homoproline amide derivatives, 15 for use in β-peptides. 16 A novel desulfurizative reduction of 3a in the presence of AgOTf also provided direct entry to the corresponding pyrazolidine 18 .…”

Inorganic‐Base‐Mediated Hydroamination of Alkenyl Oximes for the Synthesis of Cyclic Nitrones

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A method based on hydroamination mediated by inorganic base was developed for the synthesis of cyclic nitrones from alkenyl oximes. [2][3][4][5][6] Retro-Cope hydroamination of alkenyl oximes has also been studied. The transition state of this reaction is stabilized by an ionic interaction between a metal cation such as K + and the oxime oxygen and negatively charged alkene moiety.

Hydroamination of unsaturated carbon-carbon bonds (alkenes or alkynes) is one of the most efficient methods to construct nitrogen-containing heterocyclic scaffolds in an atom-and step-economical manner.

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A Cascade Synthesis of Aminohydantoins Using In Situ‐Generated N‐Substituted Isocyanates

“…Recently, we reported that amphoteric amino‐ and imino‐isocyanates can be formed in situ under mild conditions and engage in high‐yielding alkene cycloadditions6a–c and nucleophilic additions,6d,e despite their known tendency to dimerize or oligomerize 7. 8 Hydrazones6b–d and hydrazides6a,e are bench‐stable, convenient “blocked” N ‐substituted isocyanate precursors9 that form the desired isocyanates via an equilibrium induced under mild conditions, and then react with nucleophiles such as amines, alcohols, and thiols 6d–e. Using this reactivity, we developed a cascade substitution/hydroamination sequence allowing rapid assembly of saturated nitrogen heterocycles from hydrazide starting materials 6e.…”

“…Finally, N , N ‐dibenzylcarbazate 1 c (Table 1, entry 7) also cyclized in good yield. In contrast to the previous examples (LG=OPh; Table 1, entries 1–6), a temperature of 150 °C was required to ensure the formation of the amino‐isocyanate intermediate using O t Bu as a leaving group 6a. This leaving group was chosen to facilitate the synthesis of the starting material ( 1 c ), due to the lability observed during the formation of OPh derivative.…”