Abstract
磷苯□類與炔類直接進行碳－環加成反應，是一條合成雙環〔２，２，２〕辛二烯二酮類的捷徑。一般的磷苯□類很不安定容易進行雙聚反應，因此文獻上所報告的例子，大都選用四氯磷苯□或３，５－二第三丁基磷苯□３等安定的磷苯□類，與丁炔二酸二甲酯或二苯乙炔或苯炔或苯乙炔等進行環加成反應；然而，這些環加成反應為了個別在合成上的目的外，缺乏作有系統的研究。本部份，首先有系統地研究３，６－二正丙基磷苯□１和３，４－二正丙基磷苯□２等不安定磷苯□以及安定磷苯□３，分別與丁炔二酸二甲酯、二苯乙炔、苯炔、丙炔酸甲酯、苯乙炔和１－辛炔等六種帶有拉電子取代基或送電子取代基炔類之環加成反應。實驗結果發現，除了不安定磷苯□１和２分別與二苯乙炔以及１－辛炔之反應得不到加成產物外，其餘全部進行碳－環加成反應，生成雙環〔２，２，２〕辛二烯二酮類，沒有氧－環加成反應產物１，４－苯駢二氧陸環二烯類的生成，而一般磷苯□類與烯類會進行碳－環加成反應和╱或氧－環加成反應。此種差異的形成，可能在進行環加成反應時，由於炔類較烯類在直角位置多了一組（圖表省略）軌域而進一步進行次級軌域反應，造成電子效應有利於進行碳－環加成反應。又發現，不對稱取代磷苯□２和３分別與其中三種單一取代炔類進行環加成反應時，取代基會影響加成位向的選擇性，進而嘗試利用FMO 理論對此加成位向的選擇性作理論上的解釋.從立體效應，預期掩飾磷苯□類會比相對應的磷苯□類來的安定，可用來合成一些直接從磷苯□類所無法得到的加成產物；又從FMO 理論，預期掩飾磷苯□類其HOMO和LUMO中C1和C4的係數差會比相對應的磷苯□類來的大，與單一取代炔類進行環加成反應時，有較大的加成位向選擇性。基於上述理由，我們合成磷苯□１、２以及３相對應的掩飾磷苯□４、５和６以及７和８，並分別與炔類進行環加成反應，所生成的雙環〔２，２，２〕辛二烯酮類，經水解後也生成雙環〔２，２，２〕辛二烯二酮類。實驗結果發現，前面所提不安定磷苯□１和２分別與二苯乙炔以及１－辛炔反應得不到的加成產物，可經由其相對應的掩飾磷苯□４和６製得。又發現，全部得到的雙環〔２，２，２〕辛二烯二酮類加成產物，雖然經由掩飾磷苯□類比經由磷苯□類有較多的合成步驟，使得大部份加成產物的總產率較低，但是加成產物具有較大的位向選擇性，符合FMO 理論所預期的結果。從本部份的實驗結果，可以看出苯★類或掩飾★苯★類分別與炔類進行環加成反應，是合成雙環〔２，２，２〕辛二烯二酮類的好途徑。///////AbstractC-cycloaddition reactions between o-benzoquinones and acetylenes are ashortcut for synthesizing bicyclo[2,2,2]-octadiendiones. However, mosto-benzoquinones are thermally unstable at room temperature, presumablyundergoing dimerization reactions. The reported examples are only limitedto the cycloaddition reactions of stable o-benzoquinones, such astetrachloro-o-benzoquinone and 3,5-di-tert-butyl-o-benzoquinone 3, withdimethyl acetylenedicarboxylate or diphenylacetylene or benzyne orphenylacetylene for their respectively synthetic purposes. No systematicstudy has been made.In the first part of this thesis, the cycloaddition reactions of thermallyunstable 3,6-di-n-propyl-o-benzo-quinone 1 and3,4-di-n-propyl-o-benzoquinone 2 as well as thermally stable3,5-di-tert-butyl-o-benzoquinone 3 with dimethyl acetylenedicarboxylate,diphenylacetylene, benzyne, methyl propiolate, phenylacetylene and1-octyne were investigated in order to examine the substituent effects.These acetylenes were chosen due to the electron-withdrawing orelectron-donating nature of their substituents.The experimental results revealed that thermally unstable o-benzoquinones1 and 2 gave no cycloadduct with diphenyl-acetylene and 1-octyne, whileall the other cycloaddition reactions underwent C-cycloaddition to givethe corresponding bicyclo[2,2,2]octadiendiones. No O-cycloaddition adduct,1,4-benzodioxine derivative, was isolated, though most o-benzoquinonesunderwent C-cycloaddition and/or O-cyclo-addition reactions with olefins.Such difference in siteselectivities between acetylenes and olefins mayresult from the secondary molecular orbital interactions caused by theadditional orthogonal （圖表省略）and （圖表省略）of acetylenes, that is energetically more favorable for C-cycloadditionthan for O-cycloaddition. The experimental results also revealed thatsubstituents affected the regioselectivities of the cycloadditionreactions in the cases of unsymmetrically substituted o-benzoquinones 2and 3 with three monosubstituted acetylenes. Frontier molecular orbital(FMO) theory was used to rationalize the regioselectivities of thecycloaddition reactions.It was predicted that masked o-benzoquinones were more stable than thecorresponding o-benzoquinones from steric point of view and might be usedto prepare the cycloadducts that were not available directly fromo-benzoquinones. It was also predicted that the regioselectivities werelarger for masked o-benzoquinones based on the FMO theory, which predictedthat the coefficient differences between C1 and C4 in the HOMO and LUMO ofmasked o-benzoquinones were larger than those of the correspondingo-benzoquinones. Masked o-benzoquinones 4,5,6,7 and 8 were thus preparedand allowed to react with acetylenes. The cycloadducts gave bicyclo[2,2,2]octadiendiones upon hydrolyses.The results are in accord with the predictions. Thebicyclo[2,2,2]octadiendiones which were not available from thecycloaddition reactions of thermally unstable o-benzoquinones 1 and 2with diphenylacetylene and 1-octyne could be synthesized via thecorresponding masked o-benzoquinones 4 and 6. As predicted from the FMOtheory, masked o-benzoquinones show qreater regioselectivities, though theroute via masked o-benzoquinones suffers from the disadvantage of havingmore synthetic steps and this having lower overall yields.It may be concluded that the cycloaddition reactions of o-benzoquinonesand masked o-benzoquinones with acetylenes are good methods forsynthesizing bicyclo[2,2,2]octadiendiones.