An aluminum-catalyzed hydroboration of alkynes using either the commercially available aluminum hydride DIBAL-H or bench-stable Et Al⋅DABCO as the catalyst and H-Bpin as both the boron reagent and stoichiometric hydride source has been developed. Mechanistic studies revealed a unique mode of reactivity in which the reaction is proposed to proceed through hydroalumination and σ-bond metathesis between the resultant alkenyl aluminum species and HBpin, which acts to drive turnover of the catalytic cycle.
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http://dx.doi.org/10.1002/anie.201609690 | DOI Listing |
Org Lett
November 2024
Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
We describe a practical method for the synthesis of various substituted -alkyl-1,3-dihydro-2,1-benzisoxazoles and their 2,1-benzisoxazolone precursors starting from readily available methyl 2-nitrobenzoates. The method entails partial nitro reduction with hydrazine and rhodium on carbon to give the hydroxylamines, followed by base-mediated cyclization to give the corresponding benzisoxazol-3(1)-ones. Subsequent alkylation is conducted under basic conditions and is followed by reduction to the target 1,3-dihydrobenzisoxazoles, achieved with lithium aluminum hydride in the presence of trimethylsilyl chloride.
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October 2024
CNRS, ICMMO, CP3A Organic Synthesis Group, Université Paris-Saclay, 17 Avenue des Sciences, 91400, Orsay, France.
N-substituted derivatives of anti-(2R,3S)-1,3-diamino-4-phenylbutan-2-ol are important building blocks for the synthesis of therapeutically important molecules. We describe a simple protocol that allows transformation of N,N-dibenzyl-L-phenylalaninal into such compounds in only two steps. The first step is a fully stereoselective three-component MAC (Masked Acyl Cyanide) oxyhomologation reaction implicating different amines to give a panel of ten N,N-dibenzyl-O-tert-butyldimethylsilyl-protected anti-(2S,3S)-allophenylnorstatin amides.
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October 2024
G. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences, Tropinina Str. 49, Nizhny Novgorod, 603137, Russian Federation.
The interaction of aluminum hydrides [(dpp-bian)AlH] (1) and [(Ar-bian)AlH(THF)] (2) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene; Ar-bian = 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) with isocyanates RNCO (R = Ph, Cy, 3,5-ClPh) proceeds insertion of two molecules of isocyanates into each Al-H bond with the formation of unique Al carboxamides [(Ar-bian)Al{OC(H)N(R)C(NR)O}] (Ar = dpp, R = Ph, 3; Ar = Ar, R = Ph, 4; Ar = Ar, R = Cy, 5; Ar = Ar, R = 3,5-ClCH, 6). In contrast, the reactions of 1 and 2 with an excess of -butylisocyanate afford formimidate derivatives [(Ar-bian)Al{OC(H)N(Bu)}] (Ar = dpp, 7; Ar = Ar, 8). The reactions of ,'-dicyclohexylcarbodiimide with 1 and 2 give [(dpp-bian)Al{(NCy)CH}] (9) and [(Ar-bian)Al(H){(NCy)CH}] (10), correspondingly.
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October 2024
Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
This perspective highlights recent developments of the use of -heterocyclic carbenes (NHCs) and cyclic (alkyl)(amino)carbenes (cAACs) in alane and aluminum organyl chemistry. Especially in the last few years this flourishing research field led to some remarkable discoveries including various substitution patterns at the central aluminum atom, different oxidation states, neutral and charged compounds with varying coordination numbers and unique reactivities. Thereby NHCs play a vital role in the stabilization of these otherwise highly reactive compounds, which would not be realizable without the use of this intriguing class of ligands.
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December 2024
School of Integrated Biological and Chemical Sciences, University of Texas Rio Grande Valley, Brownsville, Texas, 78520, USA.
Heterometallic hydride complexes are of growing interest due to their potential to contribute to highly active insertion-based catalysis; however, methods to modulate electron density within this class of molecules are underexplored. Addition of ancillary ligands to heterotrimetallic NiAlH species (1) results in the formation of heterobimetallic NiAl-hydride complexes with varying phosphine donors (2-(L)2). Incorporation of sigma donating ancillary ligands of increasing strength led to contractions of the Ni-Al distances correlated to a strengthening of a back donation interaction to the Al-H sigma antibonding orbital, most prominently present in 2-(PMe3)2.
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