Tetra-p-cyanomethylcalix[4]arene (3) is selectively converted to its tetrabenzyl ethers 4 (1,3-alternate conformer) and 1,3-dibenzyl ethers 5 (cone conformer) by reaction with benzyl halides in the presence of variable amounts of potassium carbonate. Mono-p-cyanomethylcalix[4]arene (6) gives exclusively the cone conformer of the 1,3-disubstituted product 7 (benzyl moiety attached to the unsubstituted rings). Aroylation of 6 in the presence of sodium hydride gives tetrasubstituted product 9, whereas with aluminum chloride it produces an easily separable mixture of 1,3-disubstituted compounds 10 and 11. Surprisingly, no regioselectivity is achieved using 1-methylimidazole as the base. On the other hand, 6 reacts with 4-bromobenzenesulfonyl chloride under the same reaction conditions to produce the cone conformer of the tetrasubstituted product 12. Reactions of 6 with benzyl halides or benzaldehydes using sodium hydride as a base give the fully benzylated compounds 8 or the benzal derivatives 13, respectively.
四
氰甲基
钙克[4]
芳烃(3)在不同量的
碳酸钾存在下,与苄基卤化物反应,选择性地转化为其四
苄醚4(1,3-alternate构象)和1,3-
二苄醚5(锥构象)。单
氰甲基
钙克[4]
芳烃(6)仅生成1,3-二取代产物7的锥构象(苄基部分连接到未取代的环)。在氢化
钠存在下对6进行芳酰化反应生成四取代产物9,而与
氯化铝反应则产生易于分离的1,3-二取代化合物10和11的混合物。令人惊讶的是,使用1-甲基
咪唑作为碱时未能实现区域选择性。另一方面,6与
4-溴苯磺酰氯在相同反应条件下反应,生成四取代产物12的锥构象。使用氢化
钠作为碱,6与苄基卤化物或
苯甲醛反应,分别生成完全苄基化合物8或苄基衍
生物13。