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3.
Inorg Chem ; 63(18): 8302-8311, 2024 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-38652816

RESUMO

Diverse reactivity of the bulky tris(trimethylsilyl)silyl substituent [Si(SiMe3)3], also known as the hypersilyl group, was observed for amidinate-supported dichloro- and phenylchloroborane complexes. Treatment of the dichloroborane with potassium tris(trimethylsilyl)silyl led to the activation of the backbone ß-carbon center and formation of saturated four-membered heterocyclic chloroboranes R'{Si(SiMe3)3}C(NR)2BCl [R' = Ph, R = Cy (3); R' = Ph, R = iPr (6); R' = tBu, R = Cy (8)], whereas the four-membered amidinate hypersilyl-substituted phenyl borane 4 {PhC(NCy)2B(Ph)[Si(SiMe3)3]} was observed for the case of an amidinate-supported phenylchloroborane. The highly deshielded 11B NMR spectroscopic resonance and the distinct difference in the 29Si NMR spectrum confirmed the presence of a σ-donating hypersilyl effect on compounds 3, 6, and 8. Reaction of 3 with the Lewis acid AlCl3 led to the formation of complex 11 in which an unusual cleavage of one of the C-N bonds of the amidinate backbone is observed. Nucleophilic substitution at the boron center of saturated chloroborane 3 with phenyllithium generated the phenylborane derivative 12, whereas the secondary monomeric boron hydride 13 was observed after treatment with alane (AlH3). All compounds (2-13) have been fully characterized by NMR spectroscopy and single-crystal X-ray structure determination studies.

4.
Chem Sci ; 15(7): 2648-2654, 2024 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-38362430

RESUMO

Herein we report the B(C6F5)3-catalysed nitro-Mannich reaction between nitrones and silyl nitronates, affording silyl-protected α-nitro hydroxylamines with yields up to 99% and diastereoselectivities up to 99 : 1. Crucially, the obtained products can be converted into 1,2-diamines under simple reductive conditions. This work provides a new orthogonal method to the existing routes for the instalment of a nitro moiety under Lewis acid catalysed conditions, and expands the state-of-the-art substrate scope with respect to the silyl nitronates.

5.
Chem Sci ; 14(47): 13661-13695, 2023 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-38075657

RESUMO

The rise of CO2 concentrations in the environment due to anthropogenic activities results in global warming and threatens the future of humanity and biodiversity. To address excessive CO2 emissions and its effects on climate change, efforts towards CO2 capture and conversion into value adduct products such as methane, methanol, acetic acid, and carbonates have grown. Frustrated Lewis pairs (FLPs) can activate small molecules, including CO2 and convert it into value added products. This review covers recent progress and mechanistic insights into intra- and inter-molecular FLPs comprised of varying Lewis acids and bases (from groups 13, 14, 15 of the periodic table as well as transition metals) that activate CO2 in stoichiometric and catalytic fashion towards reduced products.

6.
Dalton Trans ; 52(44): 16118-16122, 2023 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-37901910

RESUMO

In this paper, we compare the reactivity of a series of triaryl borates B(OArx)3 as catalysts for the hydroboration of alkenes and alkynes. It was observed that commercially available B(OPh)3 performed the poorest, whereas catalysts with o-F atoms appeared to perform much better.

7.
Org Lett ; 25(3): 500-505, 2023 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-36634071

RESUMO

Herein we report a mild, transition-metal-free, highly diastereoselective Lewis acid catalyzed methodology toward the synthesis of isoxazolidine-based diazo compounds from the reaction between vinyldiazo esters and nitrones. Interestingly, the isoxazolidine products were identified to have contrasting diastereoselectivity to previously reported metal-catalyzed reactions. Furthermore, the same catalyst can be used with enol diazo esters, prompting the formation of Mukaiyama-Mannich products. These diazo products can then be further functionalized to afford benzo[b]azepine and pyrrolidinone derivatives.

8.
Dalton Trans ; 52(6): 1820-1825, 2023 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-36661186

RESUMO

A series of fluorinated triaryl borates B(OArF)3 (ArF = 2-FC6H4, 3-FC6H4, 4-FC6H4, 2,4-F2C6H3, 3,5-F2C6H3, 2,3,4-F3C6H2, 2,4,6-F3C6H2, 3,4,5-F3C6H2) have been prepared and isolated from the reactions of the mono-, di-, or tri-fluorophenol with BCl3. The Lewis acidity of these borates has been determined by NMR spectroscopic and theoretical methods and compared to their well-established borane counterpart.

9.
ACS Cent Sci ; 8(7): 855-863, 2022 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-35912338

RESUMO

Based on statistical analysis of CHN combustion results of 18 international service providers, it is determined that the ±0.4% deviation most commonly required by chemistry journals is not justified.

10.
Chemistry ; 28(45): e202201422, 2022 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-35560742

RESUMO

An efficient and mild reaction protocol for the decarbonylation of isocyanates has been developed using catalytic amounts of Lewis acidic boranes. The electronic nature (electron withdrawing, electron neutral, and electron donating) and the position of the substituents (ortho/meta/para) bound to isocyanate controls the chain length and composition of the products formed in the reaction. Detailed DFT studies were undertaken to account for the formation of the mono/di-carboxamidation products and benzoxazolone compounds.


Assuntos
Boranos , Isocianatos , Catálise , Ácidos de Lewis
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