96-32-2Relevant articles and documents
Enantioselective Allenoate-Claisen Rearrangement Using Chiral Phosphate Catalysts
Ellwart, Mario,Gensch, Tobias,Han, Seo-Jung,Lin, Hsin-Hui,Miró, Javier,Sigman, Matthew S.,Toste, F. Dean
supporting information, p. 6390 - 6399 (2020/04/27)
Herein we report the first highly enantioselective allenoate-Claisen rearrangement using doubly axially chiral phosphate sodium salts as catalysts. This synthetic method provides access to β-amino acid derivatives with vicinal stereocenters in up to 95percent ee. We also investigated the mechanism of enantioinduction by transition state (TS) computations with DFT as well as statistical modeling of the relationship between selectivity and the molecular features of both the catalyst and substrate. The mutual interactions of charge-separated regions in both the zwitterionic intermediate generated by reaction of an amine to the allenoate and the Na+-salt of the chiral phosphate leads to an orientation of the TS in the catalytic pocket that maximizes favorable noncovalent interactions. Crucial arene-arene interactions at the periphery of the catalyst lead to a differentiation of the TS diastereomers. These interactions were interrogated using DFT calculations and validated through statistical modeling of parameters describing noncovalent interactions.
Photoinduced Intermolecular [4+2] Cycloaddition Reaction for Construction of Benzobicyclo[2.2.2]octane Skeletons
Liu, Qiang,Wang, Junlei,Li, Dazhi,Yang, Chao,Xia, Wujiong
, p. 1389 - 1402 (2017/02/10)
A novel and efficient method for the synthesis of highly substituted benzobicyclo[2.2.2]octane skeletons has been explored. Under UV-light irradiation, o-divinylbenzenes underwent a pericyclic reaction to form the cyclic o-quinodimethane intermediates which were subsequently reacted with olefins through [4+2] addition to construct the benzobicyclo[2.2.2]octane skeletons in mild conditions. Gram scale reactions demonstrated the synthetic potential application of this protocol.
Phosphine-Catalyzed Domino β/γ-Additions of Benzofuranones with Allenoates: A Method for Unsymmetrical 3,3-Disubstituted Benzofuranones
Huang, Zhusheng,Yang, Xiuqin,Yang, Fulai,Lu, Tao,Zhou, Qingfa
supporting information, p. 3524 - 3527 (2017/07/17)
A phosphine-catalyzed domino process of benzofuranones with allenoates has been developed which furnishes highly functionalized unsymmetrical 3,3-disubstituted benzofuranones in synthetically useful yields. The mechanism for the transformation is a tandem β-umpolung/γ-umpolung process.
Synthesis of 1,4-enamino ketones by [3,3]-rearrangements of dialkenylhydroxylamines
Pecak, Wiktoria H.,Son, Jongwoo,Burnstine, Amy J.,Anderson, Laura L.
supporting information, p. 3440 - 3443 (2014/07/21)
The synthesis of 1,4-enamino ketones has been achieved through the [3,3]-rearrangement of dialkenylhydroxylamines generated from the addition of N-alkenylnitrones to electron-deficient allenes. The mild conditions required for this reaction, and the simultaneous installation of a fluorenyl imine N-protecting group as a consequence of the rearrangement, avoid spontaneous cyclization of the 1,4-enamino ketones to form the corresponding pyrroles and allow for the isolation and controlled divergent functionalization of these reactive intermediates. The optimization, scope, and tolerance of the new method are discussed with demonstrations of the utility of the products for the synthesis of pyrroles, 1,4-diones, and furans.
Cross-dehydrogenative coupling reactions by transition-metal and aminocatalysis for the synthesis of amino acid derivatives
Xie, Jin,Huang, Zhi-Zhen
supporting information; experimental part, p. 10181 - 10185 (2011/02/27)
The direct approach: The title coupling reactions of N-aryl glycine esters with unmodified ketones occurred smoothly in the presence of tert-butyl hydroperoxide (TBHP) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) under mild conditions (see scheme). The oxidant used for C-H activation determined the selectivity of the reactions for a particular type of ketone substrate. Copyright
Peptide ligation assisted by an auxiliary attached to amidyl nitrogen
Li, Juan,Cui, Hong-Kui,Liu, Lei
scheme or table, p. 1793 - 1796 (2010/06/13)
New thiol-containing auxiliaries were developed for peptide ligation. They were placed at the amidyl N-atom in the second amino acid residue of a peptide fragment. With the new auxiliaries, peptide ligation could be conducted at non-Cys and non-Gly sites. Compared to other recently developed auxiliaries, an important feature of the present design was that the new auxiliaries were generally applicable and readily removable.
New strategies for the design of folded peptoids revealed by a survey of noncovalent interactions in model systems
Gorske, Benjamin C.,Stringer, Joseph R.,Bastian, Brent L.,Fowler, Sarah A.,Blackwell, Helen E.
scheme or table, p. 16555 - 16567 (2010/02/15)
Controlling the equilibria between backbone cis- and trans-amides in peptoids, or N-substituted glycine oligomers, constitutes a significant challenge in the construction of discretely folded peptoid structures. Through the analysis of a set of monomeric peptoid model systems, we have developed new and general strategies for controlling peptoid conformation that utilize local noncovalent interactions to regulate backbone amide rotameric equilibria, including n→π*, steric, and hydrogen bonding interactions. The chemical functionalities required to implement these strategies are typically confined to the peptoid side chains, preserve chirality at the side chain N-α-carbon known to engender peptoid structure, and are fully compatible with standard peptoid synthesis techniques. Our examinations of peptoid model systems have also elucidated how solvents affect various side chain-backbone interactions, revealing fundamental aspects of these noncovalent interactions in peptoids that were largely uncharacterized previously. As validation of our monomeric model systems, we extended the scope of this study to include peptoid oligomers and have now demonstrated the importance of local steric and n→π* interactions in dictating the structures of larger, folded peptoids. This new, modular design strategy has guided the construction of peptoids containing 1-naphthylethyl side chains, which we show can be utilized to effectively eliminate trans-amide rotamers from the peptoid backbone, yielding the most conformationally homogeneous class of peptoid structures yet reported in terms of amide rotamerism. Overall, this research has afforded a valuable and expansive set of design tools for the construction of both discretely folded peptoids and structurally biased peptoid libraries and should shape our understanding of peptoid folding.
Alcohol-assisted phosphine catalysis: One-step syntheses of dihydropyrones from aldehydes and allenoates
Creech, Gardner S.,Kwon, Ohyun
, p. 429 - 432 (2008/09/19)
This paper describes the phosphine-catalyzed annulation of methyl allenoate with various aromatic aldehydes to form 6-aryl-4-methoxy-5,6dihydro-2-pyrones. In this reaction, the addition of an alcohol was necessary to induce dihydropyrone formation, with the optimal agent being methanol. Moreover, the addition of n-butyllithium suppressed the formation of the noncyclized product, leading to the exclusive isolation of the dihydropyrone. This method provides an efficient, one-step route toward disubstituted dihydropyrones from simple, stable starting materials.
Synthesis of 13C-labeled γ-hydroxybutyrates for EPR studies with 4-hydroxybutyryl-CoA dehydratase
Naeser, Ulrike,Pierik, Antonio J.,Scott, Richard,Cinkaya, Irfan,Buckel, Wolfgang,Golding, Bernard T.
, p. 53 - 66 (2007/10/03)
4-Hydroxybutyryl-CoA dehydratase from Clostridium aminobutyricum catalyses the reversible dehydration of its substrate 4-hydroxybutyryl-CoA (4-HB-CoA) to crotonyl CoA. The enzyme contains one [4Fe-4S]2+ cluster and one flavin adenine dinucleotide (FAD) molecule per homotetramer. Incubation of the enzyme with its substrate under equilibrium conditions followed by freezing at 77 K induced the EPR-spectrum of a neutral flavin semiquinone (g = 2.005, linewidth 2.1 mT), while at 10 K additional signals were detected. In an attempt to characterize these signals, 4-HB-CoA molecules specifically labeled with 13C have been synthesized. This was achieved via 13C- labeled γ-butyrolactones, which were obtained from 13C-labeled bromoacetic acids by efficient synthetic routes. Incubation of the 13C-labeled 4-hydroxybutyrate-CoA molecules with 4-hydroxybutyryl-CoA dehydratase did not lead to marked broadening of the signals.
Bromoacetyl bromide: A versatile and selective cleaving agent for ethers and acetals
Schneider, David F.,Viljoen, Murray S.
, p. 721 - 728 (2007/10/03)
It is shown that bromoacetyl bromide can be utilized for the selective cleavage of ethers and acetals in high yields. With cyclic ethers and acetals as starting materials, cleavage products are produced with two strategically positioned bromo substituents which may be exploited for selective extention of the carbon chain.
