通过芳磺酸酯不同化学键的可选择性断裂构建不同的芳基醚

Different Bonds Cleavage of Arenesulfonates:Access to Diverse Aryl Ethers

实现了利用芳磺酸酯作原料通过各种化学键的选择性断裂制备芳基烷基醚和二芳基醚,实现了利用吸电子基取代的芳磺酰氯与酚的反应来制备二芳基醚.在K_(2)CO_(3)作用下,分别利用酯基部分苯环上是吸电子基取代的芳磺酸芳基酯通过S―O键断裂与醇的反应,芳磺酸烷基酯通过C―O键断裂与酚的反应来合成芳基烷基醚.在K3PO4作用下,利用吸电子基取代的芳磺酸芳基酯、芳磺酰氯通过C―S键断裂与酚的反应来制备邻位具有吸电子位阻官能团的二芳基醚;此外,在缺少相应酚的情况下,上述的芳磺酸芳基酯在同样的条件下也可以得到相同的二芳基醚.

Aryl alkyl ethers and diaryl ethers represent ubiquitous structural motifs in natural products,medicinally relevant compounds,biologically active compounds,agrochemicals and organic materials,and they are also useful building blocks in organic synthesis.Therefore,many transformations have been reported for the synthesis of these two kinds of compounds.Among these versatile methods,transition-metal-free approaches using different reagents as starting materials have been developed as promising and alternative protocols.Although one example for transition-metal-catalyzed transformation of arenesulfonates into aryl alkyl ethers and diaryl ethers has been reported,there are no reports about the formation of aryl ethers utilizing arenesulfonates as starting materials via a transition-metal-free protocol,and existing methods for providing sterically hindered ortho-substituted diaryl ethers using electrophiles substituted by electron-deficient groups,particularly by a bulky one at the ortho-position as starting materials are very rare.We will report a K_(2)CO_(3)-mediated method for the synthe-sis of aryl alkyl ethers using arenesulfonates as starting materials via two alternative paths.One path is the cross-coupling of aryl arenesulfonates with alcohols through their S―O bond cleavage,and the other uses the reactions of alkyl arenesulfonates with phenols via their C―O bond cleavage.Additionally,we also report the K3PO4-promoted preparation of bulky ortho-substituted diaryl ethers via the C―S bond cleavage of aryl arenesulfonates or arenesulfonyl chlorides bearing elec-tron-withdrawing groups at 2-,2,4-or 2,6-position of the phenyl ring in the presence of phenols,respectively.General pro-cedure for the reactions of aryl arenesulfonates with various alcohols:to an oven-dried glass tube,aryl arenesulfonate 1(0.2 mmol),K2CO3(2 equiv.)and 0.5 mL alcohol 2 were added in turn.The reaction system was then stirred at 65℃until the aryl arenesulfonate 1 was completely consumed as determined by thin layer chromatography.Finally,the reaction mixture was purified by silica gel column chromatography to afford the desired product 3.General procedure for the reactions of aryl o-substituted arenesulphonates with the corresponding phenols:to an oven-dried glass tube,aryl o-substituted arenesulfonate 7(0.2 mmol),K3PO4(3 equiv.),the corresponding phenol 5(1.2 equiv.)and 1.0 mL toluene were added in turn.The reaction system was then stirred at 100℃until the reaction was over as determined by TLC.Finally,the reaction mixture was puri-fied by silica gel column chromatography to afford the desired product 8.