- Silver-Promoted Fluorination Reactions of α-Bromoamides
-
Silver-promoted C?F bond formation in α-bromoamides by using AgF under mild conditions is reported. This simple method enables access to tertiary, secondary, and primary alkyl fluorides involving biomolecular scaffolds. This transformation is applicable to primary and secondary amides and shows broad functional-group tolerance. Kinetics experiments revealed that the reaction rate increased in the order of 3°>2°>1° α-carbon atom. In addition, it was found that the acidic amide proton plays an important role in accelerating the reaction. Mechanistic studies suggested generation of an aziridinone intermediate that undergoes subsequent nucleophilic addition to form the C?F bond with stereospecificity (i.e., retention of configuration). The synthesis of sterically hindered alcohols and ethers by using AgI is also demonstrated. Examples of reactions of α-bromoamides with O nucleophiles are presented.
- Mizuta, Satoshi,Kitamura, Kanami,Kitagawa, Ayako,Yamaguchi, Tomoko,Ishikawa, Takeshi
-
supporting information
p. 5930 - 5935
(2021/02/01)
-
- Synthetic method of 2-substituted-1-(2-thiophene)-1-pentanone
-
The invention discloses a synthetic method of 2-substituted-1-(2-thiophene)-1-pentanone. The method includes the steps: taking n-pentanoic acid and bromine as raw materials, and taking phosphorus trichloride as a catalyst to prepare 2-bromovaleric acid; mixing the 2-bromovaleric acid and thionyl chloride to obtain 2-bromovaleryl chloride; taking aluminum trichloride as a catalyst, dropping thiophene into 2-bromovaleryl chloride, and stirring mixture to obtain 2-bromine-1-(2-thiophene)-1-pentanon; performing heating reflux on the 2-bromine-1-(2-thiophene)-1-pentanon and pyrrolidine or piperidine to obtain the 2-substitution-1-(2-thiophene)-1-pentanone. A target compound is a precursor compound for synthesizing drugs such as anticonvulsant drugs or vasodilator drugs and provided with an important pharmaceutical intermediate.
- -
-
Paragraph 0011
(2018/03/28)
-
- Enantioselective construction of tetrasubstituted stereogenic carbons through bronsted base catalyzed michael reactions: α′-hydroxy enones as key enoate equivalent
-
Catalytic and asymmetric Michael reactions constitute very powerful tools for the construction of new C-C bonds in synthesis, but most of the reports claiming high selectivity are limited to some specific combinations of nucleophile/electrophile compound types, and only few successful methods deal with the generation of all-carbon quaternary stereocenters. A contribution to solve this gap is presented here based on chiral bifunctional Bronsted base (BB) catalysis and the use of α′-oxy enones as enabling Michael acceptors with ambivalent H-bond acceptor/donor character, a yet unreported design element for bidentate enoate equivalents. It is found that the Michael addition of a range of enolizable carbonyl compounds that have previously demonstrated challenging (i.e., α-substituted 2-oxindoles, cyanoesters, oxazolones, thiazolones, and azlactones) to α′-oxy enones can afford the corresponding tetrasubstituted carbon stereocenters in high diastereo- and enantioselectivity in the presence of standard BB catalysts. Experiments show that the α′-oxy ketone moiety plays a key role in the above realizations, as parallel reactions under identical conditions but using the parent α,β-unsaturated ketones or esters instead proceed sluggish and/or with poor stereoselectivity. A series of trivial chemical manipulations of the ketol moiety in adducts can produce the corresponding carboxy, aldehyde, and ketone compounds under very mild conditions, giving access to a variety of enantioenriched densely functionalized building blocks containing a fully substituted carbon stereocenter. A computational investigation to rationalize the mode of substrate activation and the reaction stereochemistry is also provided, and the proposed models are compared with related systems in the literature.
- Badiola, Eider,Fiser, Bla,Gmez-Bengoa, Enrique,Mielgo, Antonia,Olaizola, Iurre,Urruzuno, Iaki,Garca, Jess M.,Odriozola, Jos M.,Razkin, Jess,Oiarbide, Mikel,Palomo, Claudio
-
supporting information
p. 17869 - 17881
(2015/02/19)
-
- Investigation of the synthetic and mechanistic aspects of the highly stereoselective transformation of α-thioamides to α-thio-β- chloroacrylamides
-
Treatment of a series of α-thioamides with N-chlorosuccinimide results in efficient transformation to the analogous α-thio-β- chloroacrylamides. The mechanistic pathway has been established through isolation and characterisation of intermediate compounds. The scope of the transformation has been explored - aryl and alkylthio substituents, primary, secondary and tertiary amides can be employed. In most instances, the chloroacrylamides are formed exclusively as the Z-stereoisomer; however, with tertiary propanamides or with amides derived from butanoic or pentanoic acid a mixture of E- and Z-stereoisomers is formed. The Royal Society of Chemistry.
- Murphy, Maureen,Lynch, Denis,Schaeffer, Marcel,Kissane, Marie,Chopra, Jay,O'Brien, Elisabeth,Ford, Alan,Ferguson, George,Maguire, Anita R.
-
p. 1228 - 1241
(2008/02/03)
-
- Mesoionic 5-alkyl-1,3-dithiolium-4-thiolates: Synthesis and brine shrimp toxicity
-
A series of twelve 1,3-dithiolium-4-thiolate mesoionic compounds were synthesized and characterized. The synthetical approach starting from α-bromoalkanoic acids to obtain the corresponding 2-N-morpholino-dithiocarbamoyl-carboxylic acids that by on-pot reaction with carbon disulfide and acetic anhydride in triethylamine formed not isolate intermediates, 1,3-dithiolium-4-olates. After, the 2-N-morpholino-5-alkyl-1,3-dithiolium-4-thiolates were obtained by retro 1,3-dipolar addition reactions. The alkyl moiety linked to C-5 of heterocyclic ring permitted the increase of the hydrophobic character and this effect was evaluated on Artemia salina lethality. The results indicated a bell-shaped relationship between the number of carbon of side chain in mesoionic derivatives and LD50 in brine shrimp toxicity assays.
- De Almeida, Paulo Afonso,Da Silva, Tania Maria Sarmento,Echevarria, Aurea
-
p. 593 - 600
(2007/10/03)
-
- A simple and efficient method of preparing α-bromo carboxylic acids
-
A new and convenient method for α-bromination of aliphatic carboxylic acids is reported. Heating carboxylic acids for 16 hours at 85 °C in trifluoroacetic acid with 1.5 equivalents of N-bromosuccinimide and a catalytic amount of concentrated H2SO4 leads to good yields of the respective α-bromocarboxylic acids.
- Zhang, Lian Hao,Duan, Jianxin,Xu, Yuelian,Dolbier Jr., William R.
-
p. 9621 - 9622
(2007/10/03)
-
- Semisynthetic Myxovirescins: Exchange of the &α-Hydroxycarboxylic Acid Segment and Modification of the Ring Size
-
Partial degradation reactions of the macrocyclic lactam-lacton antibiotic myxovirescin A1 (1) yield the key building blocks 2 and 26.From these myxovirescin analoga are reconstituted with various alkyl groups at position C-2 with R and S configuration.Furthermore a ring-contracted (24) and a ring-enlarged (29) macrocycle are synthesized.The growth of E. coli is best inhibited by the natural myxovirescin A1 with a (2S) propyl substitution whilst 24 and 29 do not inhibit the growth of E. coli at all.
- Borgschulte, Katrin,Trowitzsch-Kienast, Wolfram,Hoefle, Gerhard
-
-
