- Efficient Aryl Migration from an Aryl Ether to a Carboxylic Acid Group To Form an Ester by Visible-Light Photoredox Catalysis
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We have developed a highly efficient aryl migration from an aryl ether to a carboxylic acid group through retro-Smiles rearrangement by visible-light photoredox catalysis at ambient temperature. Transition metals and a stoichiometric oxidant and base are avoided in the transformation. Inspired by the high efficiency of this transformation and the fundamental importance of C?O bond cleavage, we developed a novel approach to the C?O cleavage of a biaryl ether to form two phenolic compounds, as demonstrated by a one-pot, two-step gram-scale reaction under mild conditions. The aryl migration exhibits broad scope and can be applied to the synthesis of pharmaceutical compounds, such as guacetisal. Primary mechanistic studies indicate that the catalytic cycle occurs by a reductive quenching pathway.
- Wang, Shao-Feng,Cao, Xiao-Ping,Li, Yang
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p. 13809 - 13813
(2017/10/24)
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- Preparation method for guacetisal
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The invention discloses a preparation method for guacetisal. The preparation method comprises the following steps: with salicylic acid as a starting material, activating salicylic acid with N,N'-carbonyldiimidazole; then reacting activated salicylic acid with guaiacol so as to obtain guaiacol salicylate; and carrying out hydroxyacetylation so as to obtain guacetisal. The preparation method provided by the invention has the following advantages: the preparation method is formulated via improvement of conventional synthetic routes; the preparation method avoids usage of reagents with great toxicity and strong irritation, such as phosphorous oxychloride, thionyl chloride and phosgene; reaction temperature is substantially lowered; reaction conditions are mild; and the method is simple to operate. It is unexpectedly discovered in the invention that a novel crystal form of guacetisal is prepared by using the preparation method; and compared with conventional crystal forms, the novel crystal form improves the water-solubility and stability of guacetisal, allows the contents of related substances to be substantially reduced, and greatly improved medication security.
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Paragraph 0071; 0072; 0078; 0079; 0085; 0086; 0094; 0095
(2017/08/29)
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- Enzymatic hydrolyses of acetoxy- and phenethylbenzoates by Candida cylindracea lipase
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The lipase from Candida cylindracea (CCL) deacctyles rapidly and selective all three regioisomer methyl acctoxybenzoates. In the enzymatic hydrolyses of analogous aryl acctoxybenzoates, the difference of reactivity between the acetoxy and benzoloxy funcionalities is reduced and a aspirin- like prodrugs. The degree of enantioselectivity of the enzymatic hydrolysis of phenethylbenzoates is related to the position of the stereogenic center.
- Cipiciani, Antonio,Fringuelli, Francesco,Scappini, Anna Maria
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p. 9869 - 9876
(2007/10/03)
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- Enzymatic and nonenzymatic in vitro hydrolysis of 2-methyl-2-[2-(methoxy)phenoxy]-4H-1,3-benzodioxin-4-one and 2-methoxyphenyl O-acetylsalicylate
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This paper is concerned with the synthesis and physical properties as well as the enzymatic and nonenzymatic in vitro hydrolysis of the potential aspirin prodrug MR 693 (5) and the salicylic acid prodrug guacetisalum (6). The half-lives of both prodrugs and the amount of aspirin regenerated in each hydrolytic run for 5 have been estimated over a wide range of pH values.
- Hundewadt,Senning
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p. 545 - 547
(2007/10/02)
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- Aspirin Prodrugs: 2-Methyl-2-aryloxy-4H-1,3-benzodioxin-4-ones Acting as True Aspirin Prodrugs
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This paper is concerned with the synthesis, physical properties and both non-enzymatic and enzymatic in vitro hydrolysis of the title compounds 5.Ten new and two known compounds 5 have been synthesized and characterized.In vitro enzymatic and non-enzymatic hydrolysis of ten compounds 5, including the two known, revealed several of them to behave as true aspirin prodrugs.
- Hundewadt, Marianne,Senning, Alexander
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p. 746 - 751
(2007/10/02)
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