摘要:光誘導(dǎo)反應(yīng)與有機(jī)金屬催化、小分子催化和不對稱催化等反應(yīng)實現(xiàn)了許多結(jié)構(gòu)復(fù)雜的雜環(huán)化合物和天然有機(jī)化合物的合成,豐富和發(fā)展了有機(jī)反應(yīng)方法學(xué)的研究內(nèi)容。在眾多的雜環(huán)化合物中,三氮唑是一類重要的具有生物和藥理活性的五元雜環(huán)化合物,被廣泛應(yīng)用于醫(yī)藥、農(nóng)藥以及其他精細(xì)化工領(lǐng)域?;诖耍撗芯恳匀〈寞B氮和苯甲酰乙腈作為原料、芘作為有機(jī)光催化劑,在可見光介導(dǎo)下,通過[3 + 2]環(huán)加成合成一系列1,4,5-取代的1,2,3-三氮唑化合物,并以核磁氫譜、碳譜、高分辨質(zhì)譜和熔點等數(shù)據(jù)對相應(yīng)目標(biāo)化合物進(jìn)行了表征。實驗結(jié)果表明:該反應(yīng)條件溫和、區(qū)域選擇性高、官能團(tuán)兼容性好,反應(yīng)操作簡單,產(chǎn)率高達(dá)99%。反應(yīng)機(jī)理揭示了該光照轉(zhuǎn)化的可能反應(yīng)歷程。該研究為1,2,3-三氮唑衍生物的合成提供了一種簡單、高效、綠色的方法,同時,豐富了三氮唑雜環(huán)化合物的分子庫。
關(guān)鍵詞:可見光催化;有機(jī)光敏劑;1,2,3-三氮唑;[3 + 2]環(huán)加成;疊氮
中圖分類號: TQ463+.53" " " " " " " " " " "文獻(xiàn)標(biāo)志碼: A文章編號: 1673-2340(2024)01-0080-07
Abstract: Photoinduced reactions, combined with organometallic catalysis, small molecule catalysis, and asymmetric catalysis, have achieved many structurally complex heterocyclic compounds and natural organic compounds, enriching, and developing the research content of organic reaction methodology. Among numerous heterocyclic compounds, triazole is an important class of five membered heterocyclic compounds with biological and pharmacological activities, widely used in pharmaceuticals, pesticides, and other fine chemical fields. Based on this, this study synthesized a series of 1,4,5-substituted 1,2,3-triazole compounds by [3+2] cycloaddition under visible light mediation, using azide and benzoylacetonitrile as raw materials and pyrene as organic photocatalysts, and the corresponding target compounds were characterized using data such as nuclear magnetic resonance H-spectroscopy, C-spectroscopy, high-resolution mass spectrometry and melting point. The experimental results show that the reaction conditions are mild, the regioselectivity is high and the functional group compatibility is good. In addition, the reaction operation is simple, the yield is as high as 99%, and the reaction mechanism reveals the potential reaction course of this photoconversion. This study provides a simple, efficient, and green method for the synthesis of 1,2,3-triazole derivatives, simultaneously enriching the molecular library of triazole heterocyclic compounds.
Key words: visible light catalysis; organic photosensitizer; 1,2,3-triazole; [3+2] cycloaddition; azides
1,2,3-三氮唑是一類重要的五元含氮雜環(huán)骨架,其衍生物具有廣泛的生物活性,如具有抗菌、抗真菌、抗吞噬、抗結(jié)核、抗病毒、抗血小板、抗炎、抗驚厥及抗腫瘤和增殖活性等功能[1-3]。到目前為止,尚未有從自然界中提取1,2,3-三氮唑結(jié)構(gòu)單元的相關(guān)報道。經(jīng)查閱文獻(xiàn)發(fā)現(xiàn),在過去幾十年里,人們?yōu)榘l(fā)展有效的制備方法作出了重大努力[4-6]。最早報道的是通過加熱經(jīng)1,3-偶極環(huán)加成合成1,2,3-三氮唑化合物[7]。然而,由于高活化能(24~26 kcal/mol),這些環(huán)加成反應(yīng)在高溫下進(jìn)行得非常緩慢,并且可能產(chǎn)生區(qū)域異構(gòu)體的混合物。同時,銅(I)催化的1,3-偶極環(huán)加成反應(yīng)也被報道。另一方面,三氮唑化合物的廣泛應(yīng)用,吸引了眾多化學(xué)工作者的研究興趣[8-13],如利用鄰疊氮芳基異腈通過銅催化的串聯(lián)反應(yīng)合成1,2,3-三氮唑[1,5-a]喹喔啉骨架衍生物。將磺基疊氮應(yīng)用于Huisgen環(huán)加成反應(yīng)中,以噻吩甲酸銅(CuTC)為催化劑在室溫下合成含磺酰基的1,2,3-三氮唑化合物。該反應(yīng)中間體很不穩(wěn)定,容易分解出氮氣得到磺酰胺類副產(chǎn)物。值得注意的是,過渡金屬銅的存在會誘導(dǎo)病毒或生物系統(tǒng)中寡核苷酸鏈的降解;此外,銅離子對生物體具有潛在的毒性。因此,這一局限性在很大程度上限制了該策略在1,2,3-三氮唑化合物制備中的應(yīng)用。因此,發(fā)展新的方法合成多取代的1,2,3-三氮唑化合物具有重要意義。
光化學(xué)反應(yīng)是指通過光引發(fā)的有機(jī)合成反應(yīng)。光敏劑、反應(yīng)中間體或底物通過吸收光子產(chǎn)生的激發(fā)態(tài)分子不同于基態(tài),其通常會發(fā)生基態(tài)分子無法參與的化學(xué)反應(yīng)。其中光催化劑對反應(yīng)起關(guān)鍵性作用,可實現(xiàn)單電子轉(zhuǎn)移(single electrontransfer,SET)[14]、氫原子轉(zhuǎn)移(hydrogen atom transfer,HAT)[15]及能量轉(zhuǎn)移(energy transfer,EnT)[16-18]。基于這些轉(zhuǎn)化過程,光催化反應(yīng)合成雜環(huán)化合物的研究取得了顯著進(jìn)展,如實現(xiàn)了酰胺、吡啶、噻吩等化合物的合成。然而,經(jīng)查閱相關(guān)文獻(xiàn)發(fā)現(xiàn),基于光催化合成1,4,5-取代的1,2,3-三氮唑化合物的研究還沒有報道。
基于之前的光催化反應(yīng)相關(guān)工作[19-20],擬在可見光介導(dǎo)的有機(jī)光敏劑催化下,以疊氮類化合物與苯甲酰乙腈類衍生物作為反應(yīng)底物,實現(xiàn)1,4,5-取代的1,2,3-三氮唑化合物的合成。
1" "實驗部分
1.1" "試劑與儀器
所有市售的藥品和溶劑在使用前都沒有經(jīng)過特殊的純化處理。芳甲酰乙腈(純度gt;97%), 安耐吉化學(xué)技術(shù)(上海)有限公司;乙腈,北京百靈威科技有限公司;碳酸鉀、芘、石油醚及乙酸乙酯,上海泰坦科技股份有限公司。光源,2 m,12 W。利用薄層層析色譜法(TLC)監(jiān)測反應(yīng)。反應(yīng)在紫外燈(254 nm或365 nm)下顯色。反應(yīng)使用合適極性的洗脫液在硅膠(300~400目)柱上進(jìn)行柱層析。核磁共振波譜均使用德國布魯克400兆核磁共振儀于室溫下測定,內(nèi)標(biāo)為三甲基硅烷,溶劑為氘代氯仿(峰的裂分模式用如下縮寫進(jìn)行描述:s = 單峰,d = 雙重峰,t = 三重峰,q = 四重峰,dd = 兩個雙重峰,m = 多重峰;耦合常數(shù)J以赫茲(Hz)表示)。所用底物按文獻(xiàn)[21]合成。
1.2" "實驗方法
在反應(yīng)管中分別加入苯甲酰乙腈(0.10 mmol)、 K2CO3(0.10 mmol)、芘(摩爾分?jǐn)?shù)為10.0%);再用注射器分別注入有機(jī)疊氮化物(0.15 mmol)和乙腈(1.0 mL);然后在室溫下通過藍(lán)光照射反應(yīng)24 h。反應(yīng)完成后萃取出有機(jī)相,再用柱層析分離純化,最終得到目標(biāo)產(chǎn)物。
1.3" "化合物表征數(shù)據(jù)
1-對甲苯基-4-氰基-5-苯基-1,2,3-三氮唑(3a):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點105~107 ℃,產(chǎn)率97%。1H NMR(400 MHz,CDCl3) δ 7.50-7.41(m,3H),7.36-7.33(m,2H), 7.27-7.20(m,4H),2.42(s,3H)。13C NMR(101 MHz,CDCl3) δ 143.0,140.7,132.8,131.0,130.3,129.4,129.0, 125.0,123.5,120.5,112.2,21.3。C16H13N4 HRMS(ESI)([M+H]+)計算值261.113 5,測試值261.113 7。
1-對甲氧基苯基-4-氰基-5-苯基-1,2,3-三氮唑(3b):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點128~130 ℃,產(chǎn)率99%。1H NMR(400 MHz,CDCl3) δ 7.51-7.42(m,3H),7.38-7.33(m,2H),7.28-7.22(m,2H),6.97-6.93(m,2H),3.86(s,3H)。13C NMR(101 MHz,CDCl3) δ 160.8,143.0,131.0,129.4, 128.9,128.1,126.6,123.5,120.3,114.8,112.2,55.7。C16H13N4O HRMS(ESI)([M+H]+)計算值277.108 4, 測試值277.108 5。
1-苯基-4-氰基-5-苯基-1,2,3-三氮唑(3c):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點119~121 ℃,產(chǎn)率94%。1H NMR(400 MHz, CDCl3) δ 7.56-7.27(m,10H)。13C NMR(101 MHz, CDCl3) δ 143.1,135.3,131.1,130.3,129.8,129.4, 129.4,129.0,125.2,125.0,123.4,120.6,112.1。C15H11N4 HRMS(ESI)([M+H]+)計算值247.097 8,測試值247.097 7。
1-對氟苯基-4-氰基-5-苯基-1,2,3-三氮唑(3d):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點99~101 ℃,產(chǎn)率70%。1H NMR(400 MHz,CDCl3) δ 7.54-7.43(m,3H),7.39-7.30(m,4H),7.21-7.13(m,2H)。13C NMR(101 MHz,CDCl3) δ 163.2(d,J = 253.5 Hz),143.1,131.4(d,J = 3.0 Hz),131.4,131.2,129.5(d, J = 62.6 Hz),128.9,127.2 (d,J = 9.1 Hz),127.1,123.1,120.7,117.1(d,J = 23.2 Hz),116.8,111.9。C15H10FN4 HRMS(ESI)([M+H]+)計算值265.088 4,測試值265.088 5。
1-對氯苯基-4-氰基-5-苯基-1,2,3-三氮唑(3e):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點121~123 ℃,產(chǎn)率96%。1H NMR (400 MHz,CDCl3) δ 7.48-7.35(m,5H),7.28-7.19(m,4H)。13C NMR(101 MHz,CDCl3) δ 142.0,135.4,132.7,130.3, 129.0,128.6,127.9,125.3,122.0,119.8,110.8。C15H10ClN4 HRMS(ESI)([M+H]+)計算值281.058 9,測試值281.059 6。
1-對溴苯基-4-氰基-5-苯基-1,2,3-三氮唑(3f):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點107~109 °C,產(chǎn)率98%。1H NMR(400 MHz,CDCl3) δ 7.63-7.45(m,5H),7.36-7.33(m,2H),7.27-7.22(m,2H)。13C NMR(101 MHz,CDCl3) δ 143.0,134.3,133.0,131.4,129.6,128.9,126.5,124.5, 123.0,120.8,111.9。C15H10BrN4 HRMS(ESI)([M+H]+)計算值325.008 4,測試值325.008 7。
1-間甲苯基-4-氰基-5-苯基-1,2,3-三氮唑(3g):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點91~93 ℃,產(chǎn)率93%。1H NMR(400 MHz,CDCl3) δ 7.52-7.42(m,3H),7.37-7.29(m,4H),7.26-7.21(m,1H),7.05-7.04(m,1H),2.38(s,3H)。13C NMR(101 MHz,CDCl3) δ 143.0,140.2,135.2, 131.1,129.4,129.4,128.9,125.7,123.4,122.2,120.5, 112.2,21.3。C16H13N4 HRMS(ESI)([M+H]+)計算值261.113 5,測試值261.113 7。
1-間溴苯基-4-氰基-5-苯基-1,2,3-三氮唑(3h):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點122~124 ℃,產(chǎn)率86%。1H NMR(400 MHz,CDCl3) δ 7.70-7.46(m,5H),7.41-7.29(m,3H),7.25-7.20(m,1H)。13C NMR(101 MHz,CDCl3) δ 143.2,136.3,133.5,131.4,130.9,129.6,129.0,128.2, 123.6,123.2,122.9,120.8,111.8。C15H10BrN HRMS(ESI)([M+H]+)計算值325.008 4,測試值325.008 4。
1-(3,5-二氯)苯基-4-氰基-5-苯基-1,2,3-三氮唑(3i):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點133~135 ℃,產(chǎn)率91%。1H NMR(400 MHz,CDCl3) δ 7.49(m,1H),7.48-7.40(m,3H),7.35-7.25(m,2H),7.21-7.15(m,2H)。13C NMR(101 MHz,CDCl3) δ 142.2,135.6,135.2,130.7,129.5, 128.8,127.9,122.6,121.5,120.0,110.5。C15H9Cl2N4 HRMS(ESI)([M+H]+)計算值315.019 9,測試值315.020 1。
1-鄰甲苯基-4-氰基-5-苯基-1,2,3-三氮唑(3j):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點126~128 ℃,產(chǎn)率49%。1H NMR (400 MHz,CDCl3) δ 7.49-7.40(m,3H),7.40-7.29(m,6H),1.97(s,3H)。13C NMR(101 MHz,CDCl3) δ 143.9,135.0, 134.5,131.7,131.0,129.4,128.9,128.3,127.4,127.3, 123.3,119.6,112.3,77.2,17.5。C16H13N4 HRMS(ESI)([M+H]+)計算值261.113 5,測試值261.113 8。
1-對甲苯基-4-氰基-5-對甲苯基-1,2,3-三氮唑(3k):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點87~89 ℃,產(chǎn)率99%。1H NMR(400 MHz,CDCl3) δ 7.27(s,1H),7.25(s,1H),7.23(s,6H),2.42 (s,3H),2.39(s,3H)。13C NMR(101 MHz,CDCl3) δ 143.1,141.5,140.6,133.0,130.3,130.1,128.8,125.0, 120.4,120.2,112.3,77.2,21.5,21.3。C17H15N4 HRMS (ESI)([M+H]+)計算值275.129 1,測試值275.129 0。
1-對甲苯基-4-氰基-5-對甲氧苯基-1,2,3-三氮唑(3l):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點114~116 ℃,產(chǎn)率97%。1H NMR (400 MHz,CDCl3) δ 7.30-7.27(m,2H),7.24(m,4H),6.95-6.90(m,2H),3.84(s,3H),2.43(s,3H)。13C NMR(101 MHz,CDCl3) δ 161.5,143.0,140.5, 133.0,130.4,130.3,125.0,119.9,115.4,114.9,112.5, 55.4,21.3。C17H15N4O HRMS(ESI)([M+H]+)計算值291.124 1,測試值291.124 0。
1-對甲苯基-4-氰基-5-對氟苯基-1,2,3-三氮唑(3m):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點101~103 ℃,產(chǎn)率78%。1H NMR(400 MHz,CDCl3) δ 7.39-7.32(m,2H),7.31-7.27(m,2H),δ 7.24-7.11(m,4H),2.43(s,3H)。13C NMR(101 MHz,CDCl3) δ 165.3,162.8,142.1,140.9,132.6,131.2(d,J = 9.1 Hz),131.1,130.4,125.0,120.4,119.6(d,J = 4.0 Hz),119.6,117.0(d,J = 22.2 Hz),116.8,112.1, 21.3。C16H12FN4 HRMS(ESI)([M+Na]+)計算值279.104 1,測試值279.104 2。
1-對甲苯基-4-氰基-5-對氯苯基-1,2,3-三氮唑(3n):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點117~119 ℃,產(chǎn)率55%。1H NMR(400 MHz,CDCl3) δ 7.36-7.33(m,2H),δ 7.22-7.19(m,4H), δ 7.14-7.12(m,2H),2.36(s,3H)。13C NMR(101 MHz,CDCl3) δ 140.9,139.9,136.5,131.6,129.43,129.2, 128.8,123.9,120.9,119.5,110.9,20.3。C16H12ClN4 HRMS(ESI)([M+H]+)計算值295.074 5,測試值295.077 4。
1-對甲苯基-4-氰基-5-對溴苯基-1,2,3-三氮唑(3o):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點131~133 ℃,產(chǎn)率50%。1H NMR(400 MHz,CDCl3) δ 7.45-7.40(m,2H),7.31-7.27(m,4H),7.21(m,2H),2.43(s,3H)。13C NMR(101 MHz,CDCl3) δ 141.9,141.0,137.5,132.6,130.5,130.2,129.8,125.0, 121.9,120.5,111.9,77.2,21.3。C16H12N4Br HRMS(ESI)([M+H]+)計算值339.024 0,測試值339.024 1。
1-對甲苯基-4-氰基-5-對甲酸甲酯苯基-1,2,3-三氮唑(3p):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點140~142 ℃,產(chǎn)率33%。1H NMR(400 MHz,CDCl3) δ 8.12-8.07(m,2H),7.45-7.40(m,2H),7.27(m,2H),7.22-7.18(m,2H),3.94(s,3H),2.43(s,3H)。13C NMR(101 MHz,CDCl3)δ 165.8,141.9,141.0,132.6,132.4,130.5,130.4,129.0, 127.7,124.9,120.8,111.8,52.6,21.3。C18H15N4O2 HRMS (ESI)([M+H]+)計算值319.119 0,測試值319.118 7。
1-對甲苯基-4-氰基-5-間甲氧苯基-1,2,3-三氮唑(3q):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點128~130 ℃,產(chǎn)率99%。1H NMR (400 MHz,CDCl3) δ 7.33(m,1H),7.27(m,2H),7.25-7.21(m,2H),7.01(m,1H),6.91-6.84(m,2H), 3.73(s,3H),2.42(s,3H)。13C NMR(101 MHz,CDCl3) δ 159.9,142.9,140.7,132.9,130.5,130.3,124.9, 124.5, 121.2,120.5,116.9,114.1,112.2,55.4,21.3。C17H15N4O HRMS(ESI)([M+H]+)計算值291.124 1,測試值291.124 4。
1-對甲苯基-4-氰基-5-間氯苯基-1,2,3-三氮唑(3r):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點137~139 ℃,產(chǎn)率86%。1H NMR(400 MHz,CDCl3) δ 7.47 (m,1H), 7.39 (m,1H), 7.33(m,1H),7.30-7.28(m,2H),7.25-7.19(m,3H),2.44(s,3H)。13C NMR(101 MHz,CDCl3) δ 159.9,142.9,140.7, 132.9,130.5,130.3,125.0,124.5,121.2,120.5,116.9, 114.1,112.2,55.4,21.3。C16H12ClN4 HRMS(ESI)([M+H]+)計算值294.074 5,測試值295.074 8。
1-對甲苯基-4-氰基-5-噻吩基-1,2,3-三氮唑(3s):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點104~106 ℃,產(chǎn)率45%。1H NMR(400 MHz,CDCl3) δ 7.50(m,2H),7.37(m,2H),7.31(m,2H),7.13-7.10(m,1H),2.49(s,3H)。13C NMR(101 MHz,CDCl3) δ 141.8,138.3,132.4,130.9,130.5,130.5,128.1, 126.3,123.5,118.9,112.4,21.5。C14H11N4S HRMS(ESI)([M+H]+)計算值267.069 9,測試值267.070 3。
1-對甲苯基-4-氰基-5-呋喃基-1,2,3-三氮唑(3t):洗脫劑V(石油醚)/V(乙酸乙酯) = 5/1,白色固體,熔點137~139 ℃,產(chǎn)率64%。1H NMR(400 MHz,CDCl3) δ 7.57(s,1H),7.41-7.32(m,4H),6.53-6.46(m,2H),2.50(s,3H)。13C NMR(101 MHz,CDCl3) δ 145.5,141.5,138.7,134.6,133.0,130.4,125.7,117.9,114.1,112.2,112.0,21.4。C14H11N4O HRMS(ESI) ([M+H]+)計算值251.092 7,測試值251.093 3。
2" "結(jié)果與討論
2.1" "反應(yīng)條件優(yōu)化
首先測試了對甲苯基疊氮化物1a與苯甲酰乙腈2a在可見光介導(dǎo)的有機(jī)光敏劑芘催化下進(jìn)行反應(yīng)的產(chǎn)率(表1)。該反應(yīng)僅以79%的產(chǎn)率提供了預(yù)期的產(chǎn)物3a(序號1)。隨后,嘗試調(diào)控1a與2a的摩爾比例,發(fā)現(xiàn)當(dāng)n(1a)∶n(2a)為1.5∶1時,收率達(dá)到最高,為97%(序號2—5)。當(dāng)降低光敏劑芘的參與量時,產(chǎn)率明顯下降為64%(序號6)。在無芘參與的可見光介導(dǎo)下,反應(yīng)收率僅有72%(序號7),而在無可見光的介導(dǎo)下,收率更低,僅60%(序號8)。同時,嘗試了芘參與的無可見光介導(dǎo)下,反應(yīng)體系以66%的收率獲得目標(biāo)產(chǎn)物(序號9)。隨后,分別嘗試了將碳酸銫、氫氧化鈉、叔丁醇鉀和磷酸鉀作為堿應(yīng)用于該反應(yīng),遺憾的是,沒有得到更好的反應(yīng)收率(序號10—13)。最后,我們嘗試了不同類型的溶劑,實驗結(jié)果表明,四氫呋喃、甲苯和二氧六環(huán)能夠促進(jìn)反應(yīng)的發(fā)生,而強(qiáng)極性的吡咯烷酮對該反應(yīng)是無效的(序號14—17)。最終確定n(1a)∶n(2a)為1.5∶1、堿為碳酸鉀、溶劑為乙腈、芘為光敏劑在12 W藍(lán)光下為最優(yōu)的反應(yīng)條件。
2.2" "反應(yīng)底物拓展
在最優(yōu)條件下,進(jìn)行了底物拓展。首先,對芳基疊氮的底物范圍進(jìn)行了探索(圖1)。實驗結(jié)果表明,當(dāng)芳基疊氮對位含取代基時,無論是吸電子還是給電子基(如對甲基、對甲氧基、對氟、對氯、對溴)均能順利參與反應(yīng),收率最高達(dá)99%(3a—3f)。對于間位取代的芳基疊氮(如間甲基、間溴和3,5-二氯),電子效應(yīng)對反應(yīng)也幾乎無影響,收率在86%~93%之間(3g—3i)。當(dāng)芳基疊氮的取代基在鄰位時(如鄰甲基),反應(yīng)收率僅為49%(3j),說明位阻對反應(yīng)影響較大。
隨后,在最優(yōu)的條件下,對芳甲酰乙腈的底物范圍進(jìn)行了探索(圖2)。由實驗數(shù)據(jù)可知,電子效應(yīng)對反應(yīng)具有一定影響,即芳甲酰乙腈對位為給電子基(如對甲基和對甲氧基)反應(yīng)效果明顯優(yōu)于吸電子基(如對氟、對氯、對溴及對甲酸甲酯),收率在33%~99%之間(3k—3p)。但對于間位取代的芳甲酰乙腈,電子效應(yīng)對反應(yīng)影響不大,如間甲氧基和間氯取代的芳甲酰乙腈參與反應(yīng)的收率分別為99% (3q)和86%(3r)。令人欣慰的是,雜芳甲酰乙腈也能順利參與反應(yīng),且收率中等(3s和3t)。
基于前期的研究工作及相關(guān)文獻(xiàn)報道,我們提出了可能的反應(yīng)機(jī)理(圖3)。首先可見光引發(fā)芘,得到激發(fā)態(tài)的芘,隨后激發(fā)態(tài)的芘通過能量傳遞,將光能轉(zhuǎn)化為內(nèi)能。芳甲酰乙腈在無機(jī)堿作用下首先去質(zhì)子化,脫去一分子H+,然后再經(jīng)互變異構(gòu),得到中間體A。隨后A與芳基疊氮進(jìn)行[3 + 2]環(huán)加成,得到中間體B,B與形成的KHCO3經(jīng)質(zhì)子交換,得到中間體B′,最后B′在堿性條件下脫去一分子水得到目標(biāo)產(chǎn)物3。
3" "結(jié)束語
綜上所述,本研究發(fā)展了一種基于可見光介導(dǎo)的有機(jī)光敏劑催化下,疊氮與苯甲酰乙腈作為底物參與[3 + 2]環(huán)加成反應(yīng)的新方法。該策略以中等至較好的收率得到了一系列1,4,5-取代的1,2,3-三氮唑化合物。該反應(yīng)體系具有條件溫和、區(qū)域選擇性高、官能團(tuán)兼容性好等優(yōu)點,為實現(xiàn)1,2,3-三氮唑衍生物的合成提供了一種有效的反應(yīng)途徑。
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(責(zé)任編輯:張燕)
收稿日期: 2023-11-28 接受日期: 2024-01-02
基金項目: 南通市科技基礎(chǔ)科學(xué)研究青年科技人才創(chuàng)新專項項目(JC12022052)
第一作者簡介: 吳亞男(1991— ), 女, 講師, 博士。
* 通信聯(lián)系人: 吳新星(1987— ), 男, 副教授, 博士, 主要研究方向為有機(jī)合成方法學(xué)。E-mail:wuxinxng@163.com