Synthetic Application of Hetero-substituted 1,3-Dienes Generated in Situ from Enone Cyclic Acetals and Dithioacetals

烯酮环状缩醛和二硫缩醛原位生成杂取代1,3-二烯的合成应用

• 批准号: 05640585
• 负责人: OHKITA Masakazu
• 金额: $ 1.28万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05640585/
• 关键词: Acetals; Enol Ethers; Diels-Alder Reaction; Dithioacetals; ディールス アルダー反応; 分子内環化付加; ディールス・アルダー反応

Recently, we have demonstrated that 2-cyclopent-1-ene ethylene acetal 1 is capable of undergoing the ring-cleavage to afford cyclopenta-1,3-dienol ether 2, which in turn is trapped by dienophiles to give 2-norbornanone ethylene acetals 4. In contrast to the corresponding keto-enol tautomerism, the thermal equilibration between cyclic acetal and its ring-opened enol ether form has been little exploited synthetically. In this study, we examined generality, selectivity, scope, and limitation of this Diels-Alder strategy. The intermediate 2 was detected by UV spectroscopy, and its content relative to 1 at a stationary state at 70ﾟC in acetonitrile was estimated to be about 0.2%. Of the several solvents examined, acetonitrile was most satisfactory. The addition reactions were highly regioselective and the 1,3-cyclopentadien-2-yl intermediates selectively derived from the corresponding acetal precursors via 1,2-elimination. Dithioacetals of 2-cyclopentenones, which are readily available from the corresponding enones, also react with dienophiles in a similar manner. The reation of dithioacetals were catalyzed with Zn (OTf) _2. The addition of ketene equivalent to (dithio) acetals allowed the convinient preparation of singly acetalized 2,5-norbornadienes.

最近，我们已经证明了2-环戊烯-1-烯缩醛1能够进行环裂解产生环戊-1,3-二烯醇醚2，而二烯醇醚2又被亲二烯试剂捕获生成2-降冰片纳米酮缩醛4。相对于相应的酮-烯醇互变异构，环缩醛与其开环烯醇醚之间的热平衡在合成上很少被利用。在这项研究中，我们检查了Diels-Alder策略的普遍性、选择性、范围和局限性。用紫外光谱法测定了中间产物2的含量，在70℃的稳定温度下，其相对于1的含量约为0.2%。在所检查的几种溶剂中，乙腈是最令人满意的。加成反应具有高度的区域选择性，1,3-环戊二烯-2-基中间体通过1,2-消去选择性地从相应的缩醛前体中衍生出来。2-环戊烯酮的二硫缩醛，很容易从相应的烯酮中得到，也以类似的方式与亲二烯试剂反应。用Zn (OTf) _2催化合成了二硫缩醛。与（双硫代）缩醛相对应的烯酮的加入，方便地制备了单缩化的2,5-降冰片二烯。

项目成果

大北 雅一: "Single Step Synthesis of Norbornan-2-one Dithioacetals from Cyclopent-2-en-1-one Dithioacetals and Dicnophiles." J.Chem.Soc.,Chem.Commun.1676-1677 (1993)

Masakazu Ohkita：“从环戊二烯-2-en-1-酮二硫缩醛和 Dicnophiles 一步合成 Norbornan-2-one 二硫缩醛。J.Chem.Soc.，Chem.Commun.1676-1677 (1993)

辻 孝: "[1.1]Paracyclophane.Generation and Spectroscopic Characterization of Bis(methoxycarbonyl)Derivative." J.Am.Chem.Soc.115. 5284-5285 (1993)

Takashi Tsuji：“[1.1]对环芳烷。双(甲氧基羰基)衍生物的生成和光谱表征。J.Am.Chem.Soc.115 (1993)。

大北 雅一: "Single Step Synthesis of 2-Norbornanone Ethylene Acetals from 2-Cyclopenten-1-one Ethylene Acetals and Dicnophiles via [2 + 4] Cycloaddition of In Situ Generated 2-(2-Hydroxyethoxy)cyclopenta-1,3-dienes and Intramolecular Reacctalization." J.Org.C

Masakazu Ohkita：“通过原位生成的 2-(2-羟基乙氧基)环戊-1,3-二烯的 [2 + 4] 环加成，从 2-环戊烯-1-酮乙缩醛和亲双酚单步合成 2-降冰片酮乙缩醛和分子内重聚。”J.Org.C