1,2-migration in<i>N</i>-phosphano functionalized<i>N</i>-heterocyclic carbenes

Kyrylchuk, Andrii; Yurchenko, A. A.; Kostyuk, Alexander; Rozhenko, Alexander

doi:10.1002/jcc.23767

Cited by 4 publications

(7 citation statements)

References 52 publications

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“…The three-membered transition state structures 1′-2′-TS are similar to the described for the isomerization of N -phosphano-functionalized N-heterocyclic carbenes (see Figure for the structures predicted for 1′a isomerization and Supporting Information for the other ones). For the SiMe 3 group migration, the lowest reaction exergonicity (Δ G – 10.4 kcal mol –1 ) and the smallest activation barrier Δ G ′ ⧧ = 20.5 kcal mol –1 were predicted for 2′a to 1′a transformation.…”

Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

“…Recently, we have studied the N → C 1,2-migration for N-phosphano-functionalized Nheterocyclic carbenes by quantum chemistry methods. 24 We have shown that the reaction proceeds via three-membered transition state structures with activation energies ΔG ⧧ and reaction energy ΔG varying in the ranges from 19 to 32 kcal mol −1 and from −13 to −26 kcal mol −1 , respectively, depending on the structure of the carbene and phosphano moiety. We used a similar approach to analyze the equilibrium between the noncyclic N-substituted carbenes 1a−k and the isomeric migration products 2a−k (Figure 2, Table 1).…”

Section: ■ Introductionmentioning

confidence: 93%

“…The reason for such easy migration is probably similar to that discussed previously for carbenes involving P(NR 2 ) 2 moieties, where it has been referred to the enhanced stability of diaminophosphenium cation as a migrating group. 24 Thus, amidine 2′i can be recommended as a potential latent carbene. In contrast, phosphorus-substituted carbenes 1′j,k require much more energy for the reversed transformation and hence can hardly be used for this purpose.…”

Section: ■ Introductionmentioning

confidence: 99%

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Latent Nucleophilic Carbenes

et al. 2021

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Using DFT and ab initio calculations, we demonstrate that noncyclic formamidines can undergo thermal rearrangement into their isomeric aminocarbenes under rather mild conditions. We synthesized the silylformamidine, for which the lowest activation energy in this process was predicted. Experimental studies proved it to serve as a very reactive nucleophilic carbene. The reactions with acetylenes, benzenes, and trifluoromethane proceeded via insertion into sp, sp2, and sp3 CH bonds. The carbene also reacted with the functional groups, such as CHO, COR, and CN at double or triple bonds, displaying high mobility of the trimethylsilyl group. The obtained silylformamidine can be considered as a latent nucleophilic carbene. It can be prepared in bulk quantities, stored, and used when the need arises. Calculation results predict similar behavior for some other silylated formamidines and related compounds.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 93%

Section: ■ Introductionmentioning

confidence: 99%

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Latent Nucleophilic Carbenes

et al. 2021

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“…1,2‐Migrations are well‐established reactions for singlet diaminocarbenes affording compounds of type B . It has been observed for various types of substituents such as alkyl,, iminoyl, dialkylamino, phosphino, borane groups,, and silicon‐containing moieties (Figure ).…”

Section: Introductionmentioning

confidence: 95%

Transformation Routes of P^V‐ and P^III‐N‐Substituted Acyclic Diaminocarbenes

et al. 2018

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Herein we report on the synthesis of a set of transient N-(P III )-phosphanyl and N-(P V )-phosphoroselenoyl acyclic diaminocarbenes by deprotonation of the corresponding formamidinium salts. It is shown that N-(P V )-substituted acyclic diaminocarbenes undergo 1,2-phosphorus shift. Transformations of N-(P III )-substituted acyclic diaminocarbenes result in tetrahydroquinazolines as final products. The proposed mechanism includes the isomerization of the carbenes into transient [a] Deprotonation of tetrasubstituted formamidinium salts is the most common approach to acyclic carbenes. Formamidinium and amidinium salts can easily be prepared using a powerful electrophilic reagent developed by Alder et al. -compounds 2 (R = Me, iPr) named in the literature as Alder's dimer. [16,17] We extended this approach on a set of formamides. Compounds 2 were readily prepared in high yields by mixing formamides 1 with triflic acid anhydride in dichloromethane (Scheme 1). The Alder's dimers usually precipitated as analytically pure compounds, in some cases recrystallization from acetonitrile was required. For these species, characteristic low-field signals (≈ 9 ppm) of CH protons were found in 1 H NMR spectra. Scheme 1. Synthesis of Alder's dimers 2.N-Aryl phosphinoselenoic amides 3 reacted readily with Alder's dimers 2a-e in 1:1 molar ratio giving salts 4a-g in over 90 % yields. [18] Their 31 P NMR chemical shift values were in a range 136-143 ppm with the 1 J PSe coupling constants (814-834 Hz) typical for the P=Se double bond. In 1 H NMR spectra CH exhibited as a doublet at 8.45-8.68 ppm with a coupling constant ca. 5 Hz or as a broad singlet. 13 C NMR signals covered the area 152-156 ppm ( 2 J CP 4-11 Hz). These P V salts were readily reduced with hexamethylphosphorus triamide to the corresponding P III formamidinium salts 5a-g (Scheme 2). Scheme 2. Synthesis of formamidinium salts 4 and 5. Deprotonation of P V -and P III -N-Substituted Formamidinium SaltsDeprotonation of P V -N-substituted formamidinium salts 4 led to the corresponding carbenes 6 that quickly underwent 1,2phosphorus shift affording the corresponding phosphane selenides 7 in high yields.In our previous article [9] we have found that deprotonation at -50°C of the salt analogous to 4a, but bearing diisopropyl-Eur.

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