1,4-雙氫口夫喃并[3,4-d]2,3-口咢口塞-2-氧化合物的合成及它在 Diels-Alder 反應上的應用

Abstract

本研究的長期目標是合成一個穩定的 non-Kekule 雙自由基分子的前驅 物,來探討雙自由基分子 (13) 的基態.在成功合成目標物 1,4-雙氫口夫 喃并[3,4-d]2,3-口咢口塞-2-氧化合物(34)(1,4-Dihydro- furano[3,4- d]2,3-oxathiin-2-oxide)後,我們同時也對此化合物進行熱化學的研究, 來探討此化合物與其異構物 4,6-雙氫口塞吩[3,4-c]口夫喃-5,5-雙氧(4 H,6H-Thieno[3,4-c]Furan-5,5-dioxide) 反應性的異同.此外,我們也合 成 1,4-雙氫-5,6-苯并-2,3-口咢口塞-2-氧化合物 (1,4-Dihydro-5,6- benzo-2,3-oxathiin-2-oxide)來建立sultine系列的研究範疇.由實驗的 結果，我們發現 1,4-雙氫口夫喃并[3,4-d] 2,3-口咢口塞-2-氫化合物 在 140℃的反應溫度範圍內，似乎遵循著 4,6 -雙氫口塞吩[3,4-c] 口夫 喃-5,5-雙氧的反應機構，也就是先進行 Diels-Alder 加成反應，然後脫 去 SO2，形成橋式 (Type A)產物。但在 N-phenylmaleimide 為親雙烯基 時，它繼續進行第二次 Diels-Alder 加成，而僅生成 Type B 產物為主 。但在更高溫度下，仍可能進行雙自由基分子的機構。然而，進一步的結 果，仍需借助於雷射瞬間光解法加以證實。而 1,4-雙氫-5,6 -苯并-2,3- 口咢口塞-2-氧化合物在150℃的反應溫度範圍內，就如文獻所述一般是先 生成二甲烯苯(o-quinodimethane)後，再進行 Diels-Alder 反應，形成 加成產物。 The long term goal of this work is to find a stable precursor for non-Kekule biradical (13) to study it's ground state mult- tiplicity. After sucessfully making our target molecule furan- sultine (1,4-Dihydrofurano[3,4-d]2,3-2-oxide; 34), we studied the thermolysis of (34) and it's isomer, furan-sulfolene (35) , in the presence and absence of alkenes and alkynes. We also studied the chemisty of benzosultine (33) for comparison. Below 140℃,uransultine (34) and furansulfolene (35) seem to follow same reaction mechanisms, i.e. firstly, they undergo Diels- Alder reactions with alkenes (or alkynes) on the furan ring and then undergo SO2 extrusion to form mostly Type A (bridged) products. In the case of N-phenylmaleimide the bridged product undergoes a second Diels-Alder reaction to form Type B compound as the only isolated product. At higher Temperature (T>140℃), however, the involvement of diradical intermediate is possible. Which needs to he proved by laser flash photolysis method. In the temperature range strdied (T≧140℃), benzosultine (33) undergoes Diels-Alder reaction via the ortho-quinodimethane intermediate (1) as described in the literatrue.