On the scope of asymmetric nitrile oxide cycloadditions with Oppolzer's chiral sultam. Total syntheses of (+)-hepialone, (-)-(1R,3R,5S)-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane, and (-)-(1S)-7,7-dimethyl-6,8-dioxabicyclo[3.2.1]octane
Highly Enantioselective Synthesis of 2,6-Disubstituted and 2,2,6-Trisubstituted Dihydropyrones: A One-Step Synthesis of (<i>R</i>)-(+)-Hepialone and Its Analogues
An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels−Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)4 (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes
通过(E)-4-甲氧基-2-三甲基甲硅烷氧基-戊-1,3-二烯(二烯1)与醛和丙酮酸的杂狄尔斯-阿尔德(HDA)反应,已经开发了一种有效的手性二氢吡喃酮的对映选择性方法。已经发现,容易获得的(R)-BINOL-Ti(O i Pr)4(1.1:1)络合物对于该反应是非常有效的催化剂。芳族,杂芳族,共轭和脂肪族醛类化合物以中等到高的分离产率(最高99%)提供了相应的产物,具有出色的对映选择性(最高99%ee)。通过二烯1的催化反应高对映选择性合成2,2,6-三取代的二氢吡喃酮的第一个例子有丙酮酸盐的报道。分离出的中间体表明该不对称的HDA反应在Mukaiyama aldol途径中进行。根据产品的绝对配置,提出了一种可能的机制。此外,该催化体系可用于合成一系列对映体富集的β-羟基酮4。最终,该方法成功地用于重要的天然产物(R)-(+)-庚烷的一步合成,分离产率为88%,对映选择性为94%。
Synthesis of hepialone; principal component from male sex scales of (lepidoptera)