Carbon−Carbon Bond Formation

2008 ◽  
Author(s):  
Jie Jack Li ◽  
Chris Limberakis ◽  
Derek A. Pflum
Keyword(s):  
Natural Products ◽  
Asymmetric Synthesis ◽  
Aldol Condensation ◽  
Bond Formation ◽  
Aldol Reaction ◽  
Aldol Reactions ◽  
Academic Press ◽  
Carbon Carbon Bond ◽  
Stereogenic Centers ◽  
Aldol Addition

Reviews: (a) Vicarion, J. L.; Badia, D.; Carillo, L.; Reyes, E.; Etxebarria, J. Curr. Org. Chem. 2005, 9, 219-235. (b) Mahrwald, R. Ed. In Modern Aldol Reactions; Wiley-VCH: Weinheim, 2004; Vol. 1., pp. 1-335 (c) Mahrwald, R. Ed. In Modern Aldol Reactions; Wiley-VCH: Weinheim, 2004; Vol. 2., pp. 1-345.(d) Machajewski, T. D.; Wong, C.-H. Angew. Chem. Int. Ed. 2000, 39, 1352-1375. (e) Carriera, E. M. In Modern Carbonyl Chemistry; Otera, J.; Wiley-VCH: Weinheim, 2000; Chapter 8: Aldol Reaction: Methodology and Stereochemistry, 227-248. (f) Paterson, I.; Cowden, C. J.; Wallace, D. J. In Modern Carbonyl Chemistry; Otera, J.; Wiley-VCH: Weinheim, 2000; Chapter 9: Stereoselective Aldol Reactions in the Synthesis of Polyketide Natural Products, pp. 249-298. (g) Franklin, A. S.; Paterson, I. Contemp. Org. Synth. 1994, 1 317-338. (h) Heathcock, C. H. In Asymmetric Synthesis; Morrison, J. D., Ed.; Academic Press: Orlando, Fl.; 1984; Vol. 3., Chapter 2: The Aldol Addition Reaction, pp. 111-212. (i) Mukaiyama, T. Org. React. 1982, 28, 203-331. Since the early 1980s, aldol condensations involving boron enolates have gain great importance in asymmetric synthesis, particularly the synthesis of natural products with adjacent stereogenic centers bearing hydroxyl and methyl groups. (Z)-Boron enolates tend to give a high diastereoslectivity preference for the syn-stereochemistry while (E)-boron enolates favor the anti-stereochemistry. Because the B-O and B-C bonds are shorter than other metals with oxygen and carbon, the six membered Zimmerman–Traxler transition state in the aldol condensation tends to be more compact which accentuates steric interactions, thus leading to higher diastereoselectivity. When this feature is coupled with a boron enolate bearing a chiral auxillary, high enantioselectivity is achieved. Boron enolates are generated from a ketone and boron triflate in the presence of an organic base such as triethylamine. Reviews: (a) Abiko, A. Acc. Chem. Res. 2004, 37, 387-395. (b) Cowden, C. J. Org. React. 1997, 51, 1-200.

scholarly journals Synthesis of a Conformationally Stable Atropisomeric Pair of Biphenyl Scaffold Containing Additional Stereogenic Centers

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 643 ◽  
Author(s):  
Chi-Tung Yeung ◽  
Wesley Chan ◽  
Wai-Sum Lo ◽  
Ga-Lai Law ◽  
Wing-Tak Wong
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Bond Formation ◽  
Aldol Reaction ◽  
Spatial Arrangement ◽  
Hydroxyl Groups ◽  
Hydrogen Bond Formation ◽  
X Ray ◽  
Stereogenic Centers ◽  
Intramolecular Hydrogen

The synthesis of a new CF3-containing stereogenic atropisomeric pair of ortho-disubstituted biphenyl scaffold is presented. The atropisomers are surprisingly conformationally stable for isolation. X-ray structures show that their stability comes from an intramolecular hydrogen bond formation from their two hydroxyl groups and renders the spatial arrangement of their peripheral CF3 and CH3 groups very different. The synthesized stereogenic scaffold proved to be effective in catalyzing the asymmetric N-nitroso aldol reaction of enamine and nitrosobenzene. Compared to similar scaffolds without CF3 groups, one of our atropisomer exhibits an increase in enantioselectivity in this reaction.

Total synthesis of pipecolic acid and 1-C-alkyl 1,5-iminopentitol derivatives by way of stereoselective aldol reactions from (S)-isoserinal

2018 ◽  
Vol 16 (7) ◽  
pp. 1118-1125 ◽  
Author(s):  
Sebastian Baś ◽  
Rafał Kusy ◽  
Monika Pasternak-Suder ◽  
Cyril Nicolas ◽  
Jacek Mlynarski ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Asymmetric Synthesis ◽  
Pipecolic Acid ◽  
Aldol Reactions ◽  
Aldol Addition

Asymmetric synthesis of the iminosugar moietyviadiastereoselective aldol addition of a pyruvate, a range of hydroxyketones and (S)-isoserinal, followed by catalytic reductive intramolecular amination.

scholarly journals Catalytic Cascade Reactions Inspired by Polyketide Biosynthesis

2020 ◽  
Vol 74 (9) ◽  
pp. 699-703
Author(s):  
Daniel Moser ◽  
Alessandro Castrogiovanni ◽  
Dominik Lotter ◽  
Reto M. Witzig ◽  
Vincent C. Fäseke ◽  
...  
Keyword(s):  
Chemical Synthesis ◽  
Bond Formation ◽  
Cascade Reactions ◽  
Aldol Reactions ◽  
Biological Functions ◽  
Polyketide Biosynthesis ◽  
Stepwise Approach ◽  
Natural Systems ◽  
Carbon Carbon Bond ◽  
Enzymatic Machinery

Aldol reactions belong to the most important methods for carbon–carbon bond formation and are also involved in one of the most astonishing biosynthetic processes: the biosynthesis of polyketides governed by an extraordinarily sophisticated enzymatic machinery. In contrast to the typical linear or convergent strategies followed in chemical synthesis, this late-stage catalysis concept allows Nature to assemble intermediates that are diversified into a broad range of scaffolds, which assume various crucial biological functions. To transfer this concept to small-molecule catalysis to access products beyond the natural systems, a stepwise approach to differentiate increasingly complex substrates was followed by investigating arene-forming polyketide cyclizations. An outline of our efforts to develop and apply these concepts are presented herein.

Ephedrines as Chiral Auxiliaries in Enantioselective Alkylation Reactions of Acyl Ephedrine Amides and Esters: A Review

2018 ◽  
Vol 15 (1) ◽  
pp. 38-83 ◽  
Author(s):  
Alejandro Cruz ◽  
Itzia I. Padilla-Martínez ◽  
Maria E. Bautista-Ramirez
Keyword(s):  
Asymmetric Synthesis ◽  
Bond Formation ◽  
Alkyl Halides ◽  
Aldol Reactions ◽  
Alkylation Reaction ◽  
Chiral Auxiliaries ◽  
Asymmetric Alkylation ◽  
Chiral Compounds ◽  
High Yields ◽  
Alkylation Reactions

Background: In modern chemistry, the asymmetric synthesis for the preparation of high purity chiral compounds to be used as pharmaceuticals or additives in foods have been of capital importance. Chiral auxiliary reagents are used to control the stereochemistry of the reaction in the generation of new chiral compounds, in this context, Ephedra compounds (ephedrines and pseudoephedrines) and some of their derivatives have been broadly used as chiral ligands in catalysis or chiral inductors in asymmetric synthesis. Objective: This review focuses on recent progress in the use of ephedra compounds and their N-substituted derivatives as chiral auxiliaries in the area of asymmetric synthesis, via the alkylation reaction of the enolates derived from their corresponding N-Acyl or O-Acyl derivatives, in the C-C bond formation. Conclusion: A vast amount of work has been done about the use of ephedra compounds in asymmetric synthesis area, in general, it was found that pseudoephedrines are much more effective than ephedrines and are preferred as chiral auxiliaries in the asymmetric alkylation of the corresponding N-acyl amides or O-Acyl esters. Alkylation with alkyl halides requires the use of more than 4 equivalents of LiCl to accelerate the alkylation rate and to complete the reaction without effecting the diastereoselectivity of the process. In contrast, the use of secondary alkyl halides was found to make the reaction very slow. Furthermore, a lot of work about the alkylation reaction in the opening of epoxides and aziridines, aldolic condensation, Manich reaction, addition of nucleophiles to α,β-unsaturated ephedrine amides and Michael additions have been demonstrated to be effective in the C-C bond formation. The aldol reaction of chiral enolates, proceeds with decreasing yields and enantioselectivities as the steric demand of the α-R of ephedrine amides and the size of carbonyl compound increase. In addition, the use of branched groups on N,N-disubstituted norephedrine esters is highly recommended in the aldol reactions of aromatic and aliphatic aldehydes.In the case of N-Acyl or O-Acyl ephedrines supported on polymers, the reaction proceed with good enantioselectivities but low yields, the enantioselectivities are goods but the yields are low. In general, the removal step of the auxiliary proceeds with low to high yields but without epimerization.

scholarly journals Biocatalytic asymmetric construction of secondary and tertiary fluorides from β-fluoro-α-ketoacids

2021 ◽  
Author(s):  
Jason Fang ◽  
Laura Turner ◽  
Michelle Chang
Keyword(s):  
Asymmetric Synthesis ◽  
Kinetic Resolution ◽  
Bond Formation ◽  
Aldol Reaction ◽  
Building Blocks ◽  
Critical Element ◽  
Type Ii ◽  
Fluorinated Building Blocks ◽  
Reaction Proceeds ◽  
New Donors

Fluorine is a critical element for the design of bioactive compounds, but its incorporation with high regio- and stereoselectivity using environmentally friendly reagents and catalysts remains an area of development. Stereogenic tertiary fluorides pose a particular synthetic challenge and are thus present in only a few approved pharmaceuticals such as fluticasone, solithromycin, and sofosbuvir. The aldol reaction of fluorinated donors provides an atom-economical approach to asymmetric C-F motifs via C-C bond formation. Here we report that the type II pyruvate aldolase HpcH and engineered mutants thereof are biocatalysts for carboligation of ß-fluoro-α-ketoacids (including fluoropyruvate, ß-fluoro-α-ketobutyrate, and ß-fluoro-α-ketovalerate) with many diverse aldehydes. The reaction proceeds with kinetic resolution in the case of racemic donors. The reactivity of HpcH towards these new donors, which are non-native in both steric and electronic properties, grants access to enantiopure fragments with secondary or tertiary fluoride stereocenters. In addition to representing the first asymmetric synthesis of tertiary fluorides via biocatalytic carboligation, the afforded products could improve the diversity of fluorinated building blocks and enable the synthesis of fluorinated drug analogs.

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