用3当量的t -BuLi处理苄基2-卤代苯基醚会同时导致锂卤交换和在苄基亚甲基上的锂化。这些二价阴离子不进行维蒂希重排,并且可以被亲电试剂捕获。它们与羧酸酯的反应提供相应的2-芳基-3-羟基-2,3-二氢苯并[ b ]呋喃,为非对映异构体的混合物。随后的酸催化或介导的脱水使各种2-芳基-3-取代的苯并[ b ]呋喃具有中等至良好的总收率。
The α-lithiobenzyloxy group, easily generated from aryl benzyl ethers by selective α-lithiation with t-BuLi at low temperature, behaves as a directed metalation group (DMG) providing a direct access to o-lithiophenyl α-lithiobenzyl ethers. This ortho-directing effect is reinforced in substrates bearing an additional methoxy group at the meta position. The generated dianions can be reacted with a selection
Wittig rearrangement and can be trapped with electrophiles. Their reactions with carboxylic esters afford the corresponding 2-aryl-3-hydroxy-2,3-dihydrobenzo[b]furans as a mixture of diastereoisomers. Subsequent acid-catalyzed or mediated dehydration gives moderate to good overall yield of a variety of 2-aryl-3-substituted benzo[b]furans.
用3当量的t -BuLi处理苄基2-卤代苯基醚会同时导致锂卤交换和在苄基亚甲基上的锂化。这些二价阴离子不进行维蒂希重排,并且可以被亲电试剂捕获。它们与羧酸酯的反应提供相应的2-芳基-3-羟基-2,3-二氢苯并[ b ]呋喃,为非对映异构体的混合物。随后的酸催化或介导的脱水使各种2-芳基-3-取代的苯并[ b ]呋喃具有中等至良好的总收率。