Ph₃PAuNTf₂ as a Superior Catalyst for the Selective Synthesis of 2<i>H</i>‐Chromenes: Application to the Concise Synthesis of Benzopyran Natural Products

Abstract

Abstract Ph 3 PAuNTf 2 (≈1 mol‐%) catalyzes the selective cycloisomerization of substituted aryl propargyl ethers into 2 H ‐chromenes in excellent yields. Benzofuran byproducts are formed only in the case of electron‐deficient arenes, in up to 7 % relative yield. The Ph 3 PAuNTf 2 ‐catalyzed cyclization of aryl propargyl ethers was applied as a key step to the concise synthesis of the naturally occurring benzopyrans seselin, xanthyletin, precocenes I and II, 8‐(3′,3′‐dimethylallyl)wenteria chromene, and 2,2‐dimethyl‐8‐prenylchromene‐6‐propenoic acid.