5,7-二甲氧基香豆素合成方法的改进

以间苯三酚为原料,选甲醇进行甲基化反应制备3,5-二甲氧基苯酚,以丙炔酸乙酯经Pechmann环化反应制备了白柠檬素(5,7-二甲氧基香豆素)。考察了甲基化反应、环化反应的影响因素,结果表明n(间苯三酚)∶n(甲醇)=1∶15,干燥氯化氢为催化剂,75℃反应7h,甲基化收率为82%;n(丙炔酸乙酯)∶n(3,5-二甲氧基苯酚)∶n(无水氯化锌)=1∶3∶1,环化温度为100℃,N2保护下反应2h,环化反应收率为88%,两步反应总收率达73%。目标产物用红外、质谱、核磁分析手段进行了表征和分析。     

1,3,5-三甲氧基苯的绿色合成工艺

以间苯三酚(PG)为原料,碳酸二甲酯(DMC)为甲基化试剂,在K2CO3/(Bu)4NBr催化下合成了1,3,5-三甲氧基苯,其结构经1H NMR,13C NMR和HR-ESI-MS确证。最佳工艺条件为:PG 10 mmol,n(DMC)∶n[(Bu)4NBr]∶n(K2CO3)∶n(PG)=12∶0.15∶1.5∶1,于160℃反应24 h,收率76.0%。     

新型苯乙酰脒类化合物的合成及其感光性能

以氢化铝锂为还原剂,甲基叔丁基醚为溶剂,1,5-二氮杂双环[4.3.0]-5-壬烯(1)于55℃反应9 h制得1,5-二氮杂双环[4.3.0]壬烷(2),收率87.9%,纯度95.0%。2分别与溴代苯乙酮(3a),对甲氧基溴代苯乙酮(3b)和对溴基溴代苯乙酮(3c)进行消除反应合成了3个新型的苯乙酰基潜双环脒类化合物(4a~4c),其结构经1H NMR和LC-MS表征。采用正交实验对合成4a~4c的反应条件进行了优化。在最佳反应条件[以甲苯为溶剂,3a 25.2 mmol,n(3a)∶n(K2CO3)∶n(2)=1.0∶2.0∶1.4,于15℃反应24 h]下,1,5-二氮杂双环[4.3.0]-5-苯乙酰基壬烷(4a)收率89.0%,纯度87.9%。感光性能研究结果表明,1,5-二氮杂双环[4.3.0]-5-(4-甲氧基)苯乙酰基壬烷(4b)经紫外曝光400 mJ·cm-1,其引发性能最强,分解转化近45%;曝光2 000 mJ·cm-1,4b分解转化近90%。     

2,5-二甲氧基-4-[(1E)-2-(1H-苯并咪唑-2-基)乙烯基]苯甲醛的合成

以2-甲基苯并咪唑(1)和2,5-二甲氧基-1,4-对苯二甲醛(3)为原料,经缩合反应合成了新化合物——2,5-二甲氧基-4-[(1E) -2-( 1H-苯并咪唑-2-基)乙烯基]苯甲醛(4),其结构经1H NMR,IR和ESI-MS表征.较佳缩合反应条件为:1 11 mol,n(1)∶n(3)=1.1∶1.0,回流反应6h,收率75.2％.     

2-氨基-4-甲氧基氯代苯甲酸的合成研究

以2-氨基-4-甲氧基苯甲酸甲酯为原料,通过氯代反应,再分别通过酯水解反应得到化合物2-氨基-5-氯-4-甲氧基苯甲酸和2-氨基-3-氯-4-甲氧基苯甲酸。其中间体及产物结构经~1H NMR、~(13)C NMR和ESI-MS确证,并考察了最佳氯代反应条件。结果表明:物料配比为n(2-氨基-4-甲氧基苯甲酸甲酯)∶n(NCS)=1∶1. 2,反应溶剂为N,N-二甲基甲酰胺,反应时间为16 h,两种氯代产物2-氨基-5-氯-4-甲氧基苯甲酸甲酯和2-氨基-3-氯-4-甲氧基苯甲酸甲酯收率分别为47%和39%。     

4-(二苯氨基)苯甲醛的合成工艺改进

以Al Cl3为催化剂,三苯氨(1)和原甲酸三乙酯(2)为原料,合成了4-(二苯氨基)苯甲醛(3),其结构经1H NMR和FT-IR确证。合成3的较佳工艺条件为:1 40 mmol,n(1)∶n(2)∶n(Al Cl3)=1∶5∶8,苯为溶剂,于30℃反应4 h,收率91%。     

4-(3,4-二甲氧基苯基)-5-硝基哌啶-2-酮的合成

以3-(3,4-二甲氧基苯基)-4-硝基丁酸甲酯(4),氨水和甲醛为原料,异丙醇溶液为溶剂,经曼尼希-酯胺解偶联反应合成了新化合物4-(3,4-二甲氧基苯基)-5-硝基哌啶-2-酮,其结构经1H NMR,13C NMR和EI-MS表征。在最佳反应条件{4 1.0 mmol,n(4)∶n(27%氨水)∶n(37%甲醛)=1.00∶1.30∶1.05,异丙醇[V(异丙醇)∶V(水)=5∶1]7.5 m L,于100℃反应12 h}下,收率74.1%。     

N-(2-吡啶甲基)取代的阿伐那非类似物的合成条件优化

以4-(3-氯-4-甲氧基苄基氨基)-2-[(2S)-2-羟甲基-1-吡咯烷基]-5-嘧啶羧酸乙酯为原料,合成了4-(3-氯-4-甲氧基苄基氨基)-2-[(2S)-2-羟甲基-1-吡咯烷基]-N-(2-吡啶甲基)-5-嘧啶甲酰胺,研究了此种阿伐那非类似物的合成条件优化,考察了投料比、反应温度、反应时间等因素对产率的影响.获得较高产率的反应条件为n(C6H8N2)∶n(C18H21ClN4O4)∶n(EDCI)∶n(HOBt)∶n(Et3N)=1.2∶1∶1.2∶1.2∶2,在搅拌下,60℃反应6h,经过后处理,柱层析纯化,得到类白色固体产物,产率为84.3%.所合成的产物经FT-IR、1 H NMR、13 C NMR、ESI-MS得到验证.     

2α-甲基-2β-溴甲基青霉烷酸二苯甲酯的合成

以6,6-二氢青霉烷酸二苯甲酯-1-氧化物(Ⅰ)和2-巯基苯并噻唑为原料,通过热裂解开环反应和溴代环合反应,制备得到了β-内酰胺酶抑制剂他唑巴坦关键中间体2α-甲基-2β-溴甲基青霉烷酸二苯甲酯(Ⅲ)。考察了反应温度、反应时间、物料比、催化剂用量对目标产物的影响。结果表明,在n(Ⅱ)∶n(HBr)∶n(Na NO_2)=1∶3∶6,催化剂质量分数为4%,-5℃反应2. 5h的条件下,收率为85. 4%。产物结构经1HNMR、FTIR、MS等技术手段得到验证。     

对甲氧基肉桂酸甲酯的一锅式绿色合成

以茴香醛(1)和丙二酸二乙酯(2)为原料,L-脯氨酸/磷酸钠为催化剂,甲醇为溶剂,经Knoenenagel缩合反应一锅式合成了对甲氧基肉桂酸甲酯。较适宜的反应条件为:141.5 mmol,n(1)∶n(2)∶n(L-脯氨酸)=1.0∶1.3∶0.3,n(L-脯氨酸)∶n(磷酸钠)=6∶1,甲醇100 mL,回流反应6 h,收率达70.2%。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.