Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts
Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts
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DOI：
10.3762/bjoc.15.43
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发表时间：
2019-02-19
影响因子：
2.7
通讯作者：
Heimgartner, Heinz
中科院分区：
文献类型：
--
作者：
Mloston, Grzegorz;Celeda, Malgorzata;Heimgartner, Heinz
金刚烷氧胺与甲醛反应生成N-(金刚烷氧基)甲醛二胺，是一种室温稳定的单体存在于溶液中的化合物。该产物用于与α-羟基亚胺酮的反应，合成了一类新的2-未取代咪唑-3-氧化物，其中N(1)上含有烷氧基。它们与2，2，4，4-四甲基半环丁烷-1，3-二硫酮或与乙酸酐的反应类似于1-烷基咪唑3-氧化物的反应，分别得到咪唑-2-硫酮和咪唑-2-酮。1-(金刚烷氧基)咪唑3-氧化物与Raney-Ni反应得到相应的咪唑类化合物，N(1)-O键没有断裂。最后，新的咪唑N-氧化物与1-溴戊烷或1-溴十二烷的O-烷基化反应打开了不同取代的、不对称的1，3-二烷氧基咪唑盐的通道。金刚烷氧胺在氢溴酸存在下与乙二醛和甲醛反应，高产率地合成了对称的1，3-二(金刚烷氧基)-1H-咪唑溴化铵。后者在元素硫存在下与三乙胺去质子化，允许原位生成相应的咪唑-2-亚甲基，该化合物捕获元素硫，生成1，3-二氢-2H-咪唑-2-硫酮作为最终产物。
Adamantyloxyamine reacts with formaldehyde to give N-(adamantyloxy)formaldimine as a room-temperature-stable compound that exists in solution in monomeric form. This product was used for reactions with alpha-hydroxyiminoketones leading to a new class of 2-unsubstituted imidazole 3-oxides bearing the adamantyloxy substituent at N(1). Their reactions with 2,2,4,4-tetramethylcy-clobutane-1,3-dithione or with acetic acid anhydride occurred analogously to those of 1-alkylimidazole 3-oxides to give imidazol-2-thiones and imidazol-2-ones, respectively. Treatment of 1-(adamantyloxy)imidazole 3-oxides with Raney-Ni afforded the corresponding imidazole derivatives without cleavage of the N(1)-O bond. Finally, the O-alkylation reactions of the new imidazole N-oxides with 1-bromopentane or 1-bromododecane open access to diversely substituted, non-symmetric 1,3-dialkoxyimidazolium salts. Adamantyloxyamine reacts with glyoxal and formaldehyde in the presence of hydrobromic acid yielding symmetric 1,3-di(adamantyloxy)-1H-imidazolium bromide in good yield. Deprotonation of the latter with triethylamine in the presence of elemental sulfur allows the in situ generation of the corresponding imidazol-2-ylidene, which traps elemental sulfur yielding a 1,3-dihydro-2H-imidazole-2-thione as the final product.