73231-34-2 An efficient enantioselective synthesis of florfenicol based on sharpless asymmetric dihydroxylation

-
An efficient and highly enantioselective synthesis of florfenicol- via a new intermediate threo-dihydroxy ester, with a Sharpless asymmetric dihydroxylation as the key step, is reported. A ring-opening/reduction strategy avoids the formation of a chlorinated byproduct that occurs in Schumachers phenyloxazoline procedure. The overall yield of florfenicol by this new process is 23% based on 4-(methylsulfonyl)benzaldehyde. Georg Thieme Verlag Stuttgart · New York. https://www.lookchem.com/CASDataBase_73231-34-2.htm

评论

发表评论

此博客中的热门博文

100-15-2 Alkyl Nitrite-Metal Halide Deamination Reactions. 7. Synthetic Coupling of Electrophilic Bromination with Substitutive Deamination for Selective Synthesis of Multiply Brominated Aromatic Compounds from Arylamines

-
Aromatic amines undergo substitution with copper(II)bromide that is in competition with substitutive deamination when these reactions are performed with tert-butyl nitrite.Except for the exceptionally reactive 4-substituted 1-aminonaphthalenes,which undergo selective bromine substitution at the 1- and 2-positions in relatively high isolated yields,rates for oxidative bromination and substitutive deamination are not sufficiently different that selective multiple bromination can be achieved.Oxidative bromination of N,N-dimethylaniline by copper(II)bromide occurs with partial dealkylation,and nitration products are observed from reactions performed with copper(II)bromide and tert-butyl nitrite.Implications of these results for the successful utilization of copper(II)bromide/tert-butyl nitrite combinations in substitutive deamination reactions of aromatic amines are discussed.Multiply brominated aromatic compounds are produced from aromatic amines in high yield through treatment of the aro...
阅读全文

75-01-4 Nickel(I) Octaethylisobacteriochlorin Anion. An Exceptional Nucleophile. Reduction and Coupling of Alkyl Halides by Anionic and Radical Processes. A Model for Factor F-430

-
Nickel(I)octaethylisobacteriochlorin anion (Ni(I)OEiBC - ) reacts extremely rapidly with aliphatic halides and methyl tosylate in homogeneous DMF solution.The reactivity sequence, CH3 > primary > secondary tertiary, and the rate law accord with an S N 2-like process for the carbon-halogen bond scission.However, the main products of the reactions derive from free radicals.The rate for methyl chloride is 2000 times faster than the corresponding reaction with the super nucleophile Co(I)B12 s -1 and the rate constant for isopropyl bromide is 350 times greater than that observed with CpFe(CO)2 - .The results indicate NiOEiBC - is the fastest nucleophile on record.Studies of the influence of solvent and reactant deuteration and the influence of anion and radical scavengers upon the product distribution suggest the intermediacy of at least one and possibly two nickel alkyls of fleeting lifetime.A novel explanation for the unusual speed of these reactions is put forward.It entails the...
阅读全文

100-64-1 On the Oxidation of Hydroxylamines with o -Iodoxybenzoic Acid (IBX)

-
o -Iodoxybenzoic acid (IBX) is confirmed as a powerful tool for the oxidation of hydroxylamines. The synthetic route is demonstrated as efficient and user friendly, and is exploited on various carbohydrate-derived N,N-disubstituted hydroxylamines (cyclic, acyclic, and functionalized ones), affording the corresponding nitrones in good yields and regioselectivity. N-Monosubstituted hydroxylamines revealed an interesting divergent behavior depending on the reaction conditions. While IBX oxidation in dimethyl sulfoxide at 45 °C furnished oximes as reported, the oxidation in dichloromethane at room temperature afforded efficiently the unusual corresponding nitroso dimers. https://www.lookchem.com/CASDataBase_100-64-1.htm
阅读全文