5281-18-5Relevant articles and documents
Large-bite diboranes for the μ(1,2) complexation of hydrazine and cyanide
Chen, Chang-Hong,Gabba?, Fran?ois P.
, p. 6210 - 6218 (2018)
As part of our interest in the chemistry of polydentate Lewis acids as hosts for diatomic molecules, we have investigated the synthesis and coordination chemistry of bidentate boranes that feature a large boron-boron separation. In this paper, we describe the synthesis of a new example of such a diborane, namely 1,8-bis(dimesitylboryl)triptycene (2) and compare its properties to those of the recently reported 1,8-bis(dimesitylboryl)biphenylene (1). These comparative studies reveal that these two diboranes feature some important differences. As indicated by cyclic voltammetry, 1 is more electron deficient than 2; it also adopts a more compact and rigid structure with a boron-boron separation (4.566(5) ?) shorter by ～1 ? than that in 2 (5.559(4) ?). These differences appear to dictate the coordination behaviour of these two compounds. While 2 remains inert toward hydrazine, we observed that 1 forms a very stable μ(1,2) hydrazine complex which can also be obtained by phase transfer upon layering a solution of 1 with a dilute aqueous hydrazine solution. The stability of this complex is further reflected by its lack of reaction with benzaldehyde at room temperature. We have also investigated the behaviour of 1 and 2 toward anions. In MeOH/CHCl3 (1/1 vol) both compounds selectively bind cyanide to form the corresponding μ(1,2) chelate complexes with a B-CN-B bridge at their cores. Competition experiments in protic media show that the anionic cyanide complex formed by 1 is the most stable, with no evidence of decomplexation even in the presence of (C6F5)3B.
Ruthenium catalyzed β-selective alkylation of vinylpyridines with aldehydes/ketonesviaN2H4mediated deoxygenative couplings
Lv, Leiyang,Li, Chao-Jun
, p. 2870 - 2875 (2021/03/14)
Umpolung (polarity reversal) tactics of aldehydes/ketones have greatly broadened carbonyl chemistry by enabling transformations with electrophilic reagents and deoxygenative functionalizations. Herein, we report the first ruthenium-catalyzed β-selective alkylation of vinylpyridines with both naturally abundant aromatic and aliphatic aldehyde/ketonesviaN2H4mediated deoxygenative couplings. Compared with one-electron umpolung of carbonyls to alcohols, this two-electron umpolung strategy realized reductive deoxygenation targets, which were not only applicable to the regioselective alkylation of a broad range of 2/4-alkene substituted pyridines, but also amenable to challenging 3-vinyl and steric-embedded internal pyridines as well as their analogous heterocyclic structures.
Solid phase submonomer azapeptide synthesis
Bowles, Maxwell,Proulx, Caroline
, p. 169 - 190 (2021/05/26)
Azapeptides contain at least one aza-amino acid, where the α-carbon has been replaced by a nitrogen atom, and have found broad applicability in fields ranging from medicinal chemistry to biomaterials. In this chapter, we provide a step-by-step protocol for the solid phase submonomer synthesis of azapeptides, which includes three steps: (1) hydrazone activation and coupling onto a resin-bound peptide, (2) chemoselective semicarbazone functionalization for installation of the aza-amino acid side chain, and (3) orthogonal deprotection of the semicarbazone to complete the monomer addition cycle. We focus on semicarbazone functionalization by N-alkylation with primary alkyl halides, and describe conditions for coupling onto aza-amino acids. Such divergent methods accelerate the synthesis of peptidomimetics and allow the rapid introduction of a wide variety of natural and unnatural side chains directly on solid support using easily accessible submonomers.
Submonomer synthesis of peptoids containingtrans-inducingN-imino- andN-alkylamino-glycines
Davern, Carolynn M.,Ison, Elon A.,Lowe, Brandon D.,Proulx, Caroline,Rosfi, Adam
, p. 8401 - 8410 (2021/06/28)
The use of hydrazones as a new type of submonomer in peptoid synthesis is described, giving access to peptoid monomers that are structure-inducing. A wide range of hydrazones were found to readily react with α-bromoamides in routine solid phase peptoid submonomer synthesis. Conditions to promote a one-pot cleavage of the peptoid from the resin and reduction to the correspondingN-alkylamino side chains were also identified, and both theN-imino- andN-alkylamino glycine residues were found to favor thetrans-amide bond geometry by NMR, X-ray crystallography, and computational analyses.
