Regioselective Addition of<i>n</i>-Alkyllithiums to α,α′-Disubstituted-1,8-Naphthyridines: Synthesis of 6-Amino-3-Pyridinol Analogs of α-Tocopherol
作者:Derek A. Pratt、Ned A. Porter、Tae-gyu Nam、Maikel Wijtmans
DOI:10.1055/s-2005-865308
日期:——
n-Alkyllithiums were added to α,α′-disubstituted-1,8-naphthyridines in non-polar solvents such as Et2O-hexane mixtures. In polar solvents such as THF, alkyllithium acts as a base rather than a nucleophile. Regioselective addition was achieved for substrates capable of five-membered cyclic chelation of the (alkyl)lithium reagent. Substrates with a TBS-protected alcohol as the co-chelating moiety afforded the best combination of yield and regioselectivity. This methodology was successfully employed in the preparation of two 6-amino-3-pyridinol analogs of pentamethylchromanol (PMC), an α-tocopherol derivative with its isoprenoid side chain truncated to a methyl group.
在非极性溶剂(如 Et2O-己烷混合物)中,将正烷基锂加入到δ,δ′-二取代的-1,8-萘啶中。在极性溶剂(如四氢呋喃)中,烷基锂充当碱而不是亲核体。对于能够与(烷基)锂试剂进行五元环螯合的底物,可实现区域选择性加成。以 TBS 保护醇作为共螯合基团的底物具有最佳的产率和区域选择性。这种方法被成功用于制备五甲基色醇(PMC)的两种 6-氨基-3-吡啶醇类似物,PMC 是一种δ-生育酚衍生物,其异戊烯侧链被截断为一个甲基。