The synthesis of novel, highly functionalized, C 2-symmetric sulfur-based catalysts is developed and their catalytic applications are explored in asymmetric bromo-, iodo- and seleno-functionalizations of alkenoicacids. This protocol provides the corresponding normal- and medium-sized bromo, iodo and selenolactones in up to 98% yield and 83% stereoselectivity.
开发了新型、高度官能化的 C 2 对称硫基催化剂的合成,并探索了它们在烯酸的不对称溴、碘和硒官能化中的催化应用。该方案以高达 98% 的产率和 83% 的立体选择性提供相应的正常和中等大小的溴、碘和硒内酯。
4-(Dimethylamino)pyridine-catalysed iodolactonisation of γ,δ-unsaturated carboxylic acids
作者:Chuisong Meng、Zhihui Liu、Yuxiu Liu、Qingmin Wang
DOI:10.1039/c5ob00806a
日期:——
4-(Dimethylamino)pyridine functioned as an excellent catalyst for iodolactonization reactions of γ,δ-unsaturated carboxylic acids, affording γ-lactones, δ-lactones, or both.
The apple never falls far from the tree: S‐alkylthiocarbamate 1 (see scheme, NBP=N‐bromophthalimide) was prepared in high yield through a synthetic sequence involving a Newman–Kwart rearrangement of the corresponding O‐alkylthiocarbamates. Compound 1 was used to catalyze bromolactonization, thus providing enantioenriched δ‐lactones in excellent yield and enantioselectivity.
A novel amino-thiocarbamate-catalyzed bromolactonization of unsaturated carboxylic acids has been developed. The scope of the reaction is evidenced by 22 examples of gamma-lactones with up to 99% yield and 93% ee. The protocol was applied in the enantioselective synthesis of the key intermediates of VLA-4 antagonists.