An attempted O-alkylation of the flexible macrocycle tetrahydroxy[3.1.3.1]metacyclophane (1) with 4-(chloromethyl) pyridine (2a) in the presence of NaH under THF reflux gave 1,3-di-O-substitution product distal-3a as a major product. In contrast, tetraol 1 was O-alkylated with 2a in the presence of Cs2CO3 to afford a mixture of two conformers of tetra-O-alkylated product 4a in a ratio of 77:23 (1,4-alternate-4a:partial-cone-4a) in 95% yield. No formation of the cone conformer in the reaction of the tetraol 1 with 2a, in comparison with those with 2-(chloromethyl) pyridine (2b) or benzyl bromide (2c) in the presence of NaH or K2CO3, which predominantly afforded cone-conformer, might be attributable to the absence of contributions derived from cationN interactions as well as cationπ interactions. The latter effect might be much smaller because of the decreased π-density of the pyridine ring compared to that of the benzene ring. The structural characterization of these products in solution as well as solid state is also discussed.Key words: macrocycles, calixarenes, cyclophanes, [3.1.3.1]metacyclophanes, O-alkylation, conformation, crystal structure, cationN interaction.
在THF回流的NaH存在下,尝试对柔性大环四羟基[3.1.3.1]甲基环辛烷(1)进行O-烷基化反应,使用4-(氯甲基)吡啶(2a)作为试剂,主要产物为1,3-二O-取代产物远端-3a。相反,在Cs2CO3存在下,用2a对四醇1进行O-烷基化反应,以77:23的比例获得两种构象的四O-烷基化产物4a混合物(1,4-交替-4a:部分锥形-4a),收率达95%。与NaH或K2CO3存在下的2-(氯甲基)吡啶(2b)或苄溴化物(2c)反应相比,没有形成四醇1与2a反应的锥形构象,这可能归因于阳离子-N相互作用和阳离子-π相互作用的缺失。后一效应可能更小,因为与苯环相比,吡啶环的π密度降低。还讨论了这些产物在溶液和固态中的结构表征。关键词:大环化合物,杯芳烃,环辛烷,[3.1.3.1]甲基环辛烷,O-烷基化,构象,晶体结构,阳离子-N相互作用。