Iodination of carbohydrate-derived 3,6-dihydro-2H-1,2-oxazines of type 3 using iodine and pyridine in DMF furnished 5-iodo-substituted 1,2-oxazine derivatives 4 with high efficacy. The alkenyl iodide moiety of 1,2-oxazine derivatives syn-4 and anti-4 was subsequently exploited for the introduction of new functionalities at the C-5 position by applying palladium-catalyzed carbon–carbon bond-forming reactions such as Sonogashira, Heck, or Suzuki coupling reactions as well as a cyanation reaction. These cross-coupling reactions led to a series of 5-alkynyl-, 5-alkenyl-, 5-aryl- and 5-cyano-substituted 1,2-oxazine derivatives being of considerable interest for further synthetic elaborations. This was exemplarily demonstrated by the hydrogenation of syn-21 and anti-24 and by a click reaction of a 5-alkynyl-substituted precursor.
使用碘和吡啶在DMF中对碳水化合物衍生的3,6-二氢-2H-1,2-噁啉(oxazines)进行碘化反应,高效地合成了5-碘取代的1,2-噁啉衍生物4。1,2-噁啉衍生物syn-4和anti-4的烯基碘醚基团随后被利用,通过钯催化的碳-碳键形成反应(如Sonogashira、Heck或Suzuki偶联反应以及氰化反应)在C-5位置引入新的官能团。这些交叉偶联反应导致了一系列具有相当重要意义的5-炔基、5-烯基、5-芳基和5-氰基取代的1,2-噁啉衍生物,这些衍生物对于进一步的合成研究具有相当的兴趣。这一点通过对syn-21和anti-24的氢化以及对一种5-炔基取代前体的click反应进行了示范。