劉亮亮, 馮乙巳,2*, 徐卓瑋, 許華建
(1. 合肥工業(yè)大學(xué) a.化學(xué)與化工學(xué)院; b. 醫(yī)學(xué)工程學(xué)院, 安徽 合肥 230009;2. 安徽省雜環(huán)實(shí)驗(yàn)室,安徽 合肥 230009)
·快遞論文·
曙紅催化的縮醛化反應(yīng)研究
劉亮亮1a, 馮乙巳1a,2*, 徐卓瑋1a, 許華建1b
(1. 合肥工業(yè)大學(xué) a.化學(xué)與化工學(xué)院; b. 醫(yī)學(xué)工程學(xué)院, 安徽 合肥 230009;2. 安徽省雜環(huán)實(shí)驗(yàn)室,安徽 合肥 230009)
以醇溶性曙紅為催化劑,在溫和條件下高效催化縮醛化反應(yīng),該催化體系適應(yīng)于不同種類的脂肪醛或芳香醛與短鏈一元醇或二元醇的羰醇縮合反應(yīng),于室溫反應(yīng)24 h,縮醛化產(chǎn)物收率58%~99%,其結(jié)構(gòu)經(jīng)1H NMR,13C NMR和HR-MS確證。
醛; 縮醛化; 醛基保護(hù); 醇溶性曙紅; 催化; 合成
醛基是一類十分活潑的化學(xué)基團(tuán),極易發(fā)生氧化、加成、聚合及縮合等反應(yīng)[1-2]。在多步合成中,為防止活潑醛基對(duì)反應(yīng)的干擾,縮醛化處理是醛基保護(hù)的最常用策略[3-4]。此外,縮醛化合物又是重要的有機(jī)中間體[5]和極具經(jīng)濟(jì)價(jià)值的化工產(chǎn)品,廣泛應(yīng)用于醫(yī)藥、食品、化妝品、香料和表面活性劑等領(lǐng)域[6]??s醛化反應(yīng)通常在質(zhì)子酸[7]催化下進(jìn)行,如硫酸、鹽酸、三氟乙酸和三氟化硼等。質(zhì)子酸來源廣泛,價(jià)格低廉,但存在催化劑用量大、催化效率低、后續(xù)處理過程復(fù)雜、腐蝕設(shè)備和污染環(huán)境等弊端。由于縮醛化反應(yīng)是可逆反應(yīng),在理論研究和工業(yè)化生產(chǎn)實(shí)踐中,縮醛化反應(yīng)在多數(shù)情況下反應(yīng)收率較低,反應(yīng)時(shí)間長,工藝過程相對(duì)復(fù)雜。有報(bào)道指出使用固體酸[8]、金屬鹽[9]和離子溶液[10]等方法,也都能獲得良好的催化效果。
近些年來,Connon等[11-12]使用含氮雜環(huán)有機(jī)鹽作為催化劑,實(shí)現(xiàn)了溫和條件下的縮醛化反應(yīng),收率41%~99%。研究發(fā)現(xiàn)一些有機(jī)小分子也能在縮醛化反應(yīng)中表現(xiàn)出良好的催化效能。如Rangel等[13]報(bào)道四氯苯醌在醇溶液和光照條件下能有效催化縮醛化反應(yīng)。推測其反應(yīng)機(jī)理認(rèn)為光激發(fā)產(chǎn)生的四氯對(duì)苯二酚起著質(zhì)子化作用,縮醛收率為47%~98%。然而該類催化劑制備復(fù)雜、價(jià)格昂貴且毒性大。
Scheme 1
醇溶性曙紅具有類似四氯對(duì)苯二酚的結(jié)構(gòu),醌酚互變的分子結(jié)構(gòu)(Chart 1)具有質(zhì)子化作用,并表現(xiàn)出較強(qiáng)的酸性??s醛化反應(yīng)的實(shí)質(zhì)是質(zhì)子化過程。本文對(duì)曙紅催化的縮醛化反應(yīng)進(jìn)行研究,發(fā)現(xiàn)該催化體系在不同種類的脂肪醛或芳香醛與短鏈一元醇或二元醇的羰醇縮合反應(yīng)中具有良好的催化活性,于室溫反應(yīng)24 h,縮醛化產(chǎn)物收率58%~99%(Scheme 1),其結(jié)構(gòu)經(jīng)1H NMR,13C NMR和HR-MS確證。
Chart 1
1.1 儀器與試劑
安捷倫VNMRS600型超導(dǎo)核磁共振儀(CDCl3為溶劑,TMS為內(nèi)標(biāo));Waters LCT Premier XE型高分辨質(zhì)譜儀;Trace 1300型氣相色譜儀。
HSGF254高效薄層層析硅膠板,煙臺(tái)匯友開發(fā)有限公司;HSGF254型薄層板硅膠(300~400 目),青島海洋化工分廠;其余所用試劑均為分析純或化學(xué)純。
1.2 縮醛化反應(yīng)合成3a~3p(以3a為例)
在Schlenk反應(yīng)管中依次加入苯甲醛(1a)53 mg(0.5 mmol), 1 mol%醇溶性曙紅3.2 mg和甲醇(2a)2 mL,攪拌下于室溫反應(yīng)24 h(GC監(jiān)測)。用飽和NaHSO3溶液(5 mL)洗滌除去殘留苯甲醛,依次用飽和NaHCO3溶液(5 mL)和蒸餾水洗滌,無水Na2SO4干燥,旋蒸脫溶后經(jīng)硅膠柱層析[洗脫劑:V(石油醚)∶V(乙酸乙酯)=20 ∶1]純化得淡黃色液體苯甲醛二甲縮醛(3a)70 mg,收率92%。
用類似方法合成3b~3p,其中含強(qiáng)吸電子基的對(duì)硝基苯甲醛(1b)在微熱條件反應(yīng),其余醛類于室溫反應(yīng)。
3a: 淡黃色液體,收率92%;1H NMRδ: 7.46~7.44(s, 2H, ArH), 7.36(d,J=7.1 Hz, 2H, ArH), 7.32(t,J=7.2 Hz, 1H, ArH), 5.39(s, 1H, CH), 3.33(s, 6H, CH3);13C NMRδ: 137.99, 128.41, 128.16, 126.64, 103.11, 52.67; HR-MSm/z: Calcd for C9H12O2[M+] 152.084 6, found 152.084 2。
對(duì)甲氧基苯甲醛二甲縮醛(3b): 淡黃色液體,收率88%;1H NMRδ: 7.37(d,J=8.5 Hz, 2H, ArH), 6.89(d,J=8.6 Hz, 2H, ArH), 5.35(s, 1H, CH), 3.81(s, 3H, OCH3), 3.31(s, 6H, CH3);13C NMRδ: 159.66, 130.37, 127.89, 113.51, 103.05, 55.18, 52.59; HR-MSm/z: Calcd for C10H14O3[M+]182.091 4, found 182.091 2。
對(duì)硝基苯甲醛二甲縮醛(3c): 淡黃色液體,收率98%;1H NMRδ: 8.22~8.24(s, 2H, ArH), 7.64~7.65(s, 2H, ArH), 5.48 (s, 1H, CH), 3.34 (s, 6H, CH3);13C NMRδ: 148.02, 145.06, 127.81, 123.42, 101.57, 52.71; HR-MSm/z: Calcd for C9H11NO4[M+]197.072 0, found 197.072 2。
對(duì)氯苯甲醛二甲縮醛(3d): 淡黃色液體,收率95%;1H NMR(DMSO-d6)δ: 7.44(d,J=8.5 Hz, 2H, ArH), 7.39(d,J=8.4 Hz, 2H, ArH), 5.39(s, 1H, CH), 3.23(s, 6H, CH3);13C NMR(DMSO-d6)δ: 137.19, 132.95, 128.44, 128.18, 101.85, 52.57; HR-MSm/z: Calcd for C9H11O2Cl[M+] 186.046 4, found 186.046 0。
間溴苯甲醛二甲縮醛(3e): 淡黃色液體,收率92%;1H NMR(DMSO-d6)δ: 7.55~7.53 (m, 1H, ArH), 7.39 (d,J=7.8 Hz, 1H, ArH), 7.36 (t,J=7.6 Hz, 1H, ArH), 5.39 (s, 1H, CH), 3.25(s, 6H, CH3);13C NMR(DMSO-d6)δ: 138.05, 131.22, 130.42, 129.21, 125.57, 122.39, 101.63, 52.70; HR-MSm/z: Calcd for C9H11O2Br[M+] 229.996 8, found 229.996 6。
間甲基苯甲醛二甲縮醛(3f): 淡黃色液體,收率90%;1H NMR(DMSO-d6)δ: 7.26(t,J=7.5 Hz, 1H, ArH), 7.20(s, 1H, ArH), 7.18~7.13(m, 2H, ArH), 5.33(s, 1H, CH), 3.23(s, 6H, CH3), 2.32(s, 3H, CH3);13C NMR(DMSO-d6)δ: 138.09, 137.18, 127.94, 127.01, 126.85, 123.56, 102.69, 52.46, 20.67; HR-MSm/z: Calcd for C10H14O2[M+]166.102, found 166.103 4。
鄰氯苯甲醛二甲縮醛(3g): 淡黃色液體,收率94%;1H NMR(DMSO-d6)δ: 7.68(d,J=8.5 Hz, 1H, ArH), 7.39(d,J=8.4 Hz, 1H, ArH), 7.28(s, 1H, ArH), 7.21(s, 1H, ArH), 5.36(s, 1H, CH), 3.37(s, 6H, CH3);13C NMR(DMSO-d6)δ: 137.21, 132.85, 129.24, 128.34, 128.28, 126.52, 101.75, 52.52; HR-MSm/z: Calcd for C9H11O2Cl [M+]186.043 4, found 186.043 2。
對(duì)硝基苯甲醛二乙縮醛(3h): 淡黃色液體,收率82%;1H NMRδ: 8.22(d,J=8.6 Hz, 2H, ArH), 7.66(d,J=8.3 Hz, 2H, ArH), 5.58(s, 1H, CH), 3.59(dt,J=16.4 Hz, 9.3 Hz, 4H, CH2), 1.25(t,J=7.0 Hz, 6H, CH3);13C NMRδ: 147.90, 146.10, 127.71, 123.39, 100.12, 61.27, 15.13; HR-MSm/z: Calcd for C11H15NO4[M+]225.108 6, found 225.108 8。
2-(4-硝基苯基)-1,3-二氧戊環(huán)(3i): 淡黃色液體,收率97%;1H NMRδ: 8.25(s, 2H, ArH), 7.66(s, 2H, ArH), 5.90(s, 1H, CH), 4.15~4.07(m, 4H, CH2);13C NMRδ: 148.35, 144.88, 127.40, 123.57, 102.21, 65.46: HR-MSm/z: Calcd for C9H9NO4[M+]195.053 6, found 195.053 2。
苯乙醛二甲基縮醛(3j): 無色液體,收率80%;1H NMRδ: 7.30(d,J=7.6 Hz, 2H, ArH), 7.24(s, 2H, ArH), 7.21(d,J=7.2 Hz, 1H, ArH), 4.54(t,J=5.6 Hz, 1H, CH), 3.34(s, 6H, CH3), 2.91(s, 2H, CH2);13C NMRδ: 137.03, 129.40, 128.29, 126.34, 105.34, 53.31, 39.67; HR-MSm/z: Calcd for C10H14O2[M+]166.102 8, found 166.102 4。
苯丙醛二甲基縮醛(3k): 無色液體,收率86%;1H NMRδ: 7.28(t,J=7.5 Hz, 2H, ArH), 7.21~7.17(m, 3H, ArH), 4.37(t,J=5.7 Hz, 1H, CH), 3.33(s, 6H, CH3), 2.70~2.65(m, 2H, CH2), 1.93(dt,J=13.7 Hz, 5.9 Hz, 2H, CH2);13C NMRδ: 141.61, 128.37, 125.85, 103.76, 52.71, 34.08, 30.85; HR-MSm/z: Calcd for C11H16O2[M+]180.125 3, found 180.125 1。
苯乙醛二乙基縮醛(3l): 無色液體,收率58%;1H NMRδ: 7.24~7.20(m, 2H, ArH), 7.19(s, 2H, ArH), 7.17(d,J=7.7 Hz, 1H, ArH), 4.57(t,J=5.6 Hz, 1H, CH), 3.64~3.59(m, 2H, CH2), 3.42~3.35(m, 2H, CH2), 2.86(d,J=5.6 Hz, 2H, CH2), 1.10(t,J=7.0 Hz, 6H, CH3);13C NMRδ: 137.35, 129.59, 128.14, 126.24, 103.85, 61.86, 40.89, 15.25; HR-MSm/z: Calcd for C12H18O2[M+]194.136 6, found 194.136 4。
苯丙醛二乙基縮醛(3m): 無色液體,收率64%;1H NMRδ: 7.30~7.27(m, 2H, ArH), 7.22(d,J=7.6 Hz, 2H, ArH), 7.20(d,J=7.3 Hz, 1H, ArH), 4.51(t,J=5.7 Hz, 1H, CH), 3.68(dq,J=14.2 Hz, 7.1 Hz, 2H, CH2), 3.52(dq,J=14.3 Hz, 7.1 Hz, 2H, CH2), 2.74~2.68(m, 2H, CH2), 2.00~1.94(m, 2H, CH2), 1.24(t,J=7.1 Hz, 6H, CH3);13C NMRδ: 141.78, 128.39, 128.34, 125.78, 102.19, 61.02, 35.09, 31.01, 15.37; HR-MSm/z: Calcd for C13H20O2[M+]208.151 5, found 208.151 3。
1,1-二甲氧基辛烷(3n): 無色液體,收率82%;1H NMRδ: 4.35(t,J=5.7 Hz, 1H, CH), 3.30(s, 6H, CH3), 1.58(dd,J=14.6 Hz, 6.1 Hz, 2H, CH2), 1.36~1.21(m, 12H, CH2), 0.87(t,J=6.9 Hz, 3H, CH3);13C NMRδ: 104.60, 52.57(s), 32.50, 31.77, 29.44, 29.21, 24.60, 22.63, 14.06; HR-MSm/z: Calcd for C10H22O2[M+]174.163 4, found 174.163 6。
1,1-二甲氧基壬烷(3o): 無色液體,收率77%;1H NMRδ: 4.35(t,J=5.7 Hz, 1H, CH), 3.40(d,J=105.5 Hz, 6H, CH3), 1.60(ddd,J=14.6 Hz, 11.0 Hz, 6.4 Hz, 2H, CH), 1.26(dd,J=20.1 Hz, 9.2 Hz, 10H, CH), 0.87(t,J=6.9 Hz, 3H, CH3);13C NMRδ: 104.59, 52.56, 32.50, 31.85, 29.50(2C), 29.21, 24.60, 22.65, 14.08; HR-MSm/z: Calcd for C11H24O2[M+]188.183 5, found 188.183 3。
1,1-二甲氧基庚烷(3p): 無色液體,收率86%;1H NMRδ: 4.36(t,J=5.8 Hz, 1H, CH), 3.32(s, 6H, CH3), 1.62~1.56(m, 2H, CH2), 1.30(dd,J=12.2 Hz, 5.6 Hz, 6H, CH2), 1.28(s, 2H, CH2), 0.88(t,J=6.8 Hz, 3H, CH3);13C NMRδ: 104.50, 52.54, 32.45, 31.76, 29.14, 24.56, 22.57, 14.07; HR-MSm/z: Calcd for C9H20O2[M+]160.152 7, found 160.152 5。
2.1 反應(yīng)條件優(yōu)化
以1a與2a的縮醛化反應(yīng)為模型反應(yīng),研究催化劑及其用量和反應(yīng)時(shí)間等因素對(duì)縮醛化反應(yīng)的影響,對(duì)反應(yīng)條件進(jìn)行優(yōu)化,結(jié)果見表1。
研究了水溶性曙紅與醇溶性對(duì)1a與2a的縮醛化反應(yīng),選用類似于四溴苯醌和四溴對(duì)苯二酚結(jié)構(gòu)的曙紅催化劑。從表1實(shí)驗(yàn)結(jié)果可推測:具有類似四溴苯酚結(jié)構(gòu)的醇溶性曙紅,有明顯的催化效果(No.3);醌結(jié)構(gòu)的水溶性曙紅沒有表現(xiàn)出催化作用(No.2)。這與Rangel等[10]的實(shí)驗(yàn)結(jié)果相一致,他們選用四氯苯醌作為催化劑,在光照條件下四氯苯醌轉(zhuǎn)化四氯對(duì)苯二酚,四氯苯醌沒有催化活性,起催化作用的是四氯對(duì)苯二酚。醇溶性曙紅本身具有類似四氯對(duì)苯二酚的結(jié)構(gòu),在無光條件下即可實(shí)現(xiàn)縮醛化的高效催化。本文進(jìn)一步探究了催化劑用量和反應(yīng)時(shí)間的影響,可以看出1 mol%(No.4)是最佳的催化劑量,減少催化劑量時(shí),收率下降(No.5~6),增加催化劑量時(shí),收率無顯著提高(No.3);選擇8~36 h進(jìn)行模型反應(yīng)時(shí),分析實(shí)驗(yàn)結(jié)果發(fā)現(xiàn):24 h是最優(yōu)的反應(yīng)時(shí)間(No.4),縮短反應(yīng)時(shí)間收率下降(No.7~8),延長反應(yīng)時(shí)間收率無進(jìn)一步提升。通過對(duì)模型反應(yīng)的各類影響因素的優(yōu)化和篩選,確定苯甲醛與甲醇縮醛化反應(yīng)的最佳條件為:1 mol%醇溶性曙紅為催化劑,在無水甲醇(2 mL)中于室溫反應(yīng)24 h,收率94%。
表1 模型反應(yīng)條件優(yōu)化*
*反應(yīng)條件: 1a 0.5 mmol, 2a 2 mL,于室溫反應(yīng)。
2.2 底物適應(yīng)性
由Scheme 1反應(yīng)結(jié)果可知,醇溶性曙紅作為催化劑具有良好的底物適應(yīng)性。首先模型反應(yīng)可以獲得92%的收率(3a)。對(duì)于取代苯甲醛,無論是具有吸電子基Cl, Br和NO2,或是具有供電子基CH3和OCH3,縮醛化反應(yīng)都獲得較高的反應(yīng)收率(3b~3g),并呈現(xiàn)出一定的反應(yīng)規(guī)律。苯甲醛對(duì)位為吸電子基時(shí),收率相對(duì)模型反應(yīng)升高,幾乎獲得定量反應(yīng)的收率(3c~3d);苯甲醛對(duì)位為供電子基時(shí),收率相對(duì)模型反應(yīng)下降(3b)。對(duì)于間位取代的苯甲醛,無論是供電子基還是吸電子基,其收率相比模型反應(yīng)差別不大(3e~3f),主要是由于間位的空間位阻作用和電子效應(yīng)影響不明顯。當(dāng)吸電子基位于醛基鄰位時(shí),縮醛化收率相比模型反應(yīng)稍微增加(3g),主要是電子效應(yīng)與空間效應(yīng)共同作用的結(jié)果。對(duì)于不同的脂肪醛,醇溶性曙紅也表現(xiàn)出良好的催化效能,但由于烷基是供電子基團(tuán),其反應(yīng)收率相比于苯甲醛有所下降(3f~3l)。本文進(jìn)一步研究使用不同短鏈一元醇(如甲醇和乙醇)或二元醇(如乙二醇)進(jìn)行的縮醛化反應(yīng),其中醇類起到反應(yīng)物和溶劑作用。乙醇由于碳骨架比甲醇長,其反應(yīng)收率會(huì)出現(xiàn)明顯的下降(如3c和3h)。乙二醇由于與醛形成是穩(wěn)定的環(huán)狀結(jié)構(gòu),其收率相比乙醇較高。
選用廉價(jià)易得的有機(jī)分子曙紅作為催化劑,通過反應(yīng)條件的優(yōu)化和底物適應(yīng)范圍的探究,實(shí)現(xiàn)縮醛化合物的高效合成。實(shí)驗(yàn)結(jié)果表明:苯甲醛在室溫條件下的甲醇溶液中反應(yīng)24 h可達(dá)到92%的縮醛收率。該反應(yīng)底物適用范圍廣泛,當(dāng)選用不同類型的芳香醛和脂肪醛時(shí),縮醛化反應(yīng)都能獲得很好的收率;對(duì)于不同種類的短鏈一元醇和二元醇的羰醇縮合反應(yīng),醇溶性曙紅也表現(xiàn)出良好的兼容性。曙紅催化劑具有優(yōu)良的反應(yīng)特性,縮醛合成在室溫或微熱條件下進(jìn)行,催化劑用量少,反應(yīng)溫和且高效。該研究結(jié)果為縮醛香料的合成提供一種簡單經(jīng)濟(jì)的新方法,溫和高效且底物適應(yīng)范圍廣,具有一定的工業(yè)應(yīng)用前景。
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Study on The Acetalization Reaction Catalyzed by Eosin Y
LIU Liang-liang1a, FENG Yi-si1a,2*, XU Zhuo-wei1a, XU Hua-jian1b
(a. School of Chemistry and Chemical Engineering; b. School of Medical Egineering; 1. Hefei University of Technology, Hefei 230009, China; 2. Anhui Provincial Laboratory of Heterocyclic Chemistry, Hefei 230009, China)
The acetalization reaction of different kinds of aliphatic aldehydes or aromatic aldehydes with short chain monohydric alcohols and diols was achieved under mild conditions catalyzed by the alcohol-soluble Eosin Y. The yield of acetal compounds were 58%~99% after reaction for 24 h at room temperature. The structures were confirmed by1H NMR,13C NMR and HR-MS.
aldehyde; acetalization; carbonyl protection; alcohol-soluble Eosin Y; catalysis; synthesis
2016-04-12;
2016-11-16
國家自然科學(xué)基金資助項(xiàng)目(21472033, 21371044)
劉亮亮(1989-),男,漢族,安徽界首人,碩士研究生,主要從事有機(jī)合成研究。 E-mail: d30914038@126.com
馮乙巳,教授, Tel. 0551-62904405, E-mail: fengyisi@hfut.edu.cn
O621.3; O623.54+1
A
10.15952/j.cnki.cjsc.1005-1511.2017.01.16100