A Regioselective Lithiation of ortho-Cresols Using the Bis(dimethylamino)phosphoryl Group as a Directing Group: General Synthesis of 2,3-Dihydrobenzo(b)furans Including Naturally Occurring Neolignans.
作者:Mituaki WATANABE、Kenji KAWANISHI、Ryuji AKIYOSHI、Sunao FURUKAWA
DOI:10.1248/cpb.39.3123
日期:——
A general synthetic method was developed for 2-aryl-2, 3-dihydrobenzo[b]furans via regioselective lithiation of ortho-tolyl tetramethylphosphorodiamidates followed by addition of aromatic aldehydes as a key step. ortho-Tolyl tetramethylphosphorodiamidates were regioselectively lithiated with sec-BuLi in tetrahydrofuran at -105°C to give benzylic lithio species. The resulting lithio species were reacted with aromatic aldehydes to provide 1, 2-diarylethanolderivatives. Reductive removal of the phosphoryl group with lithium aluminum hydride followed by acidic treatment led to 2-aryl-2, 3-dihydrobenzo[b]furans in good overall yields. The utility of this strategy was demonstrated in regioselective syntheses of highly substituted neolignan natural products, such as (±)-licarin B and (±)-carnatol, starting from O-bis(dimethylamino)phosphorylated eugenol or isoeugenol.
作为关键步骤,通过对原甲苯基四甲基磷二酰胺进行区域选择性石化作用,然后加入芳香醛,开发了一种 2-芳基-2,3-二氢苯并[b]呋喃的通用合成方法。生成的二硫代锂与芳香醛反应,得到 1,2-二硫代乙醇衍生物。用氢化铝锂还原去除磷基,然后进行酸处理,可得到 2-芳基-2,3-二氢苯并[b]呋喃,总产率很高。在以 O-双(二甲基氨基)磷酸化丁香酚或异丁香酚为起始物,对 (±)-licarin B 和 (±)-carnatol 等高度取代的新木犀草素天然产物进行区域选择性合成时,证明了这一策略的实用性。