Alkylthio acrylates

Hydrogel Polymers from Alkylthio Acrylates for Biomedical Applications... 

Introduction of an alkylthio group on the allene system increased the reactivity of the allene moiety in [2 + 2] cycloaddition reactions. It proved possible to conduct reactions of this allene at much lower temperatures. By adding Lewis acids, the reaction temperature could be decreased even more, as was illustrated by the Lewis acid catalyzed [2-1-2] cycioadditions of l-trimethylsilyl-l-methylthio-l,2-propadiene with a variety of electron-poor alkenes, including cyclic and non-cyclic enones, acrylates, methyl fumarate and acrylonitrile. When a chiral diol 21 based titanium catalyst was employed, the [2-1-2] cycloaddition reactions of /-acryloyl-l,3-oxazolidin-2-ones 17a and 17b with allenyl sulfides 18 yielded methylenecyclobutanes 19 and 20 with high optical purities (equation The highest yields were obtained with electron-poor allenophile 17b. 

Several methods for making pyrroles involve in situ generation of azomethine ylides and anions. In the presence of electrophilic acetylenes these can be trapped and converted to pyrroles. One source of azomethine ylides are A -(a-trimethylsilylmethyl) derivatives of imidates and thioimidates. Azomethine ylides are generated by desilylation with fluoride ion. The salts are obtained by N-alkylation of imidate esters <83TL4303> or S-alkylation of thioacetamides <86JOCi997>. The alkoxy or alkylthio groups are eliminated after cycloaddition. Electrophilic alkenes such as dimethyl maleate, dimethyl fumarate, maleonitrile and methyl acrylate give A -pyrrolenines (Scheme 80). 

Modifications of the C(2)-position are limited due to synthetic difficulties associated with direct introduction substituents at C-2. However, the synthesis of 2-phenylsubstituted fluoroquinolones has been developed [55], and6-fluoro-quinolon-2-carboxylic acids have been obtained by cychzation of the corresponding 2-amino-substituted 3-pentafluorobenzoyl acrylic acids [56], 2-Thio substituted quinolones are widely used for the synthesis [a]- or [b]-annelated fluoroquinolones, such as thiazolo-and azethydinoquinolones [57-59]. Synthesis of l-cyclopropyl-2-alkylthio-8-methoxyfluoroquinolones was described however elucidation of their antibacterial activity revealed no regularities associated with incorporation of 2-alkylthio substituents [60], AU known 2-aza analogues of quinolones and naphthyridines, derivatives of cinnohne, have not exhibited any remarkable antibacterial activity. 

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