Swain Nigel A, Brown Richard C D, Bruton Gordon
Department of Chemistry, The University of Southampton, Highfield, Southampton SO17 1BJ, U.K.
J Org Chem. 2004 Jan 9;69(1):122-9. doi: 10.1021/jo035365r.
A new stereoselective route to endo,exo-2,6-diarylfurofuranones has been developed using Mn(III)-mediated intramolecular cyclopropanation and C-H insertion reactions as key C-C bond-forming steps. Mn(III)-mediated oxidative cyclization of acetoacetate derivative 11 afforded 1-acetyl-4-aryl-3-oxabicyclo[3.1.0]hexan-2-one (12) with excellent diastereocontrol (d.r. 22:1). Subsequent Lewis acid-catalyzed opening of the activated cyclopropane ring present in 12 with benzylic alcohols then gave alpha-acetyl-gamma-butyrolactones 16 and 18-20, which reacted efficiently with in situ-generated TfN(3) to secure the key alpha-diazo-gamma-butyrolactones 22-25. Highly stereoselective rhodium-catalyzed C-H insertion reactions of diazolactones 22-25 completed the synthesis of endo,exo-2,6-diarylfurofuranones 26-29 in overall yields ranging from 41 to 48% from 1-phenylallyl alcohol (+/-)-10. The approach developed for the furofuranones 26-29 was then applied to the asymmetric syntheses of four furofuran lignans, (+)-xanthoxylol (1), (+)-methylxanthoxylol (2), (+)-epipinoresinol (3), and (+)-epieudesmin (4), starting from enantiomerically enriched 1-arylallyl alcohol (S)-31.
已开发出一种新的立体选择性合成内型、外型-2,6-二芳基呋喃酮的路线，该路线使用锰(III)介导的分子内环丙烷化反应和C-H插入反应作为关键的碳-碳键形成步骤。锰(III)介导的乙酰乙酸酯衍生物11的氧化环化反应以优异的非对映选择性（非对映体比例为22:1）得到1-乙酰基-4-芳基-3-氧杂双环[3.1.0]己烷-2-酮(12)。随后，用苄醇对12中存在的活化环丙烷环进行路易斯酸催化开环反应，得到α-乙酰基-γ-丁内酯16以及18 - 20，它们与原位生成的三氟甲磺酸叠氮化物(TfN(3))高效反应，得到关键的α-重氮-γ-丁内酯22 - 25。重氮内酯22 - 25的高度立体选择性铑催化C-H插入反应完成了内型、外型-2,6-二芳基呋喃酮26 - 29的合成，从1-苯基烯丙醇(±)-10出发，总收率为41%至48%。然后将开发的用于合成呋喃酮26 - 29的方法应用于四种呋喃呋喃木脂素(+)-花椒毒素(1)、(+)-甲基花椒毒素(2)、(+)-表松脂醇(3)和(+)-表桉叶素(4)的不对称合成，起始原料为对映体富集的1-芳基烯丙醇(S)-31。
