3-位环庚烷(酰)基取代的焦脱镁叶绿酸-a甲酯的合成

以焦脱镁叶绿酸-a甲酯(MPP-a)为起始原料, 在对其E-环羰基进行保护的前提下, 经焦脱镁叶绿酸-d甲酯与环庚基溴化镁进行Grignard反应; 所生成新的卟吩仲醇再经脱保护、脱水和氧化等诸多反应, 将3-位仲羟基转化成碳碳双键和羰基, 其碳氧双键再行Grignard反应并脱水成烯, 完成一系列未见报道的3-位环庚基取代的焦脱镁叶绿酸-a甲酯衍生物的合成. 其化学结构均经UV, IR, ¹H NMR及元素分析予以证实.     

焦脱镁叶绿酸的Knoevenagel反应及其杂环取代衍生物的合成

以焦脱镁叶绿酸-d甲酯(MPPd)为起始原料, 通过其醛基与连有五元杂环的β-二酮、α-氰基酮和丙二腈的活性亚甲基进行Knoevenagel反应, 完成3-位五元杂环取代的焦脱镁叶绿酸-a甲酯衍生物. 所合成的新化合物均经UV, IR, ¹H NMR及元素分析证明其结构.     

具有叶绿素-a基本骨架的20-meso-位取代二氢卟吩衍生物的合成

以脱镁叶绿酸-a甲酯(MPa)为起始原料,分别与氯化、溴化和硫酸重氮苯进行偶联反应,其主要产物为20-卤素取代或者亚硝基取代的二氢卟吩,仅以微量产率的得到期待的产物.焦脱镁叶绿酸的锌配合物与3-N,N-二甲胺基丙烯醛的Vilsmeier反应生成20-甲酰乙烯基焦脱镁叶绿酸.焦脱镁叶绿酸-d与N-溴代丁二酰亚胺(NBS)的溴代反应生成单一的20-溴代产物,再经Wittig反应恢复乙烯基而得到20-溴代焦脱镁叶绿酸-a甲酯.其它叶绿素降解产物的亲电取代反应均以较好的产率得到生成的20-meso-位取代的二氢卟吩衍生物.首次报道的具有叶绿素基本碳架的二氢卟吩衍生物的化学结构均经UV,IR,1H NMR及元素分析得以证实.     

脱镁叶绿酸-a甲酯的1,3-偶极环加成及其叶绿素衍生物的合成

以脱镁叶绿酸-a甲酯(1)为起始原料, 利用其3-位乙烯基与重氮甲烷的1,3-偶极环加成反应, 得到3-位氢化吡唑取代的脱镁叶绿酸-a衍生物2, 通过热裂解使得3-位吡唑基开环并重排成环丙基. 碱性条件下, 所生成的3-环丙基取代的卟吩3脱甲氧甲酰基后转化成焦脱镁叶绿酸衍生物4. 选用重氮乙烷为另一偶极体与1进行1,3-偶极环加成反应, 则给出2-甲基环丙基取代的立体异构体卟吩5, 同样经过脱甲氧甲酰基处理, 得到焦脱镁叶绿酸衍生物6. 所合成新叶绿素衍生物2～6均经UV, IR, ¹H NMR及元素分析证明其结构.     

焦脱镁叶绿酸的炔化反应及其叶绿素类二氢卟吩的合成

以焦脱镁叶绿酸-a甲酯为起始原料,利用加成和氧化反应将其转化成3-甲酰基或者3-乙酰基取代和E-环保护的反应前体,通过Grignard反应在3-位上引进炔基并构建了叔醇或者仲醇结构,再经脱水和氧化反应生成端位烯炔和炔酮取代的二氢卟吩衍生物.3-甲酰基焦脱镁叶绿酸-a甲酯与癸基溴化镁的Grignard反应、E-保护和C(3)-羟基的氧化反应得到C(3)-长链烷酰基取代的焦脱镁叶绿酸-a甲酯,再经酸催化脱水则得到含有链间烯炔结构的二氢卟吩.首次报道的叶绿素类二氢卟吩衍生物均经UV,IR,1H NMR及元素分析确定其化学结构,对相应的化学反应也提出了可能的反应机理.     

3-位长链烷基双(单)取代焦脱镁叶绿酸-a甲酯的合成

以焦脱镁叶绿酸-a甲酯(1)为起始原料, 通过E环保护和3-位乙烯基的氧化反应得到卟吩醛2, 与长链烷基溴化镁的Grignard反应将3-位甲酰基转化为1-羟长链烷基, 选用TPAP和N-甲基吗啉N-氧化物混合氧化剂对卟吩仲醇3的羟基进行氧化, 生成3-位烷酰基焦脱镁叶绿酸-a衍生物4, 再与长链烷基溴化镁进行Grignard反应, 得到亲核加成产物卟吩叔醇5和还原产物3; 以对甲苯磺酸催化, 卟吩醇3和5在干燥苯中回流脱水, 分别给出反式结构的3-位长链烷基单或者双取代的焦脱镁叶绿酸-a甲酯衍生物6和7. 所合成的叶绿酸衍生物均经UV, IR, ¹H NMR及元素分析证明其结构.     

焦脱镁叶绿酸-a甲酯的溴化反应

以焦脱镁叶绿酸-a甲酯为起始原料,通过与各种溴化剂的加成和取代反应,在3-位和meso-位上引进溴原子,分别得到单取代、三取代和四取代的溴化卟吩;其3-位乙烯基与溴化氢的加成则分别生成正常溴代产物和水解产物及其酯化产物.用四氧化锇和高碘酸钠将焦脱镁叶绿酸甲酯的3-位乙烯基氧化成醛,进而与四溴化碳和三苯基磷反应,生成3-位偕二溴取代焦脱镁叶绿酸衍生物.所合成的叶绿酸溴代衍生物均经UV, IR, 1H NMR及元素分析证明其结构.     

氢氧化锂存在下(焦)脱镁叶绿酸-a甲酯的空气重排反应

在氢氧化锂存在下, 脱镁叶绿酸-a甲酯(1a)发生空气氧化和重排反应, 经盐酸酸化和重氮甲烷甲基化, 得到由紫红素-7三甲酯(2)、紫红素-18甲酯(3)、卟吩-p₆三甲酯(4)、地质卟啉衍生物(5)和3-环氧乙基-3-去乙烯基紫红素-18甲酯(6)所组成的混合物. 用相同的方法处理焦脱镁叶绿酸-a甲酯(1b), 则分离出13²-氧代焦脱镁叶绿酸-a甲酯(7)、15-甲酰基紫红素-5二甲酯(8)、紫红素-18甲酯(3)和3-环氧乙基-3-去乙烯基紫红素-18甲酯(6). 所得新叶绿素衍生物5, 6和8的化学结构均经UV, IR, ¹H NMR及元素分析得以证实, 并对相应的反应提出可能的反应机理.     

3-位苯并含氮杂环取代的焦脱镁叶绿酸-α甲酯的合成

以焦脱镁叶绿酸-a甲酯(MPP-a)(1)为起始原料,在二氯甲烷中与醋酸锌共回流得锌配合物2,在四氯钯锂催化下,通过与苯基氯化汞的偶联反应生成3b-苯基焦脱镁叶绿酸-a甲酯(3).分别选用四氧化锇、高钌酸四丙基铵(TPAP)和N-甲基吗啉N-氧化物将环外烯键氧化成邻二酮(4).在酸性条件下,4与邻苯二胺的缩合形成了3-位喹喔啉取代的焦脱镁叶绿酸-a甲酯(5).用四氧化锇和高碘酸钠将l的3-位碳碳双键氧化,则生成焦脱镁叶绿酸-d甲酯(6).所得卟吩醛与环己二酮和萘胺进行一锅法反应,得到3-位苯并吖啶取代的焦脱镁叶绿酸-a甲酯(7).所合成的新卟吩化合物均经UV,IR,1H NMB及元素分析证明其结构.     

C(3)-乙烯基的化学修饰与含氧基团取代的叶绿素-a衍生物的合成

以焦脱镁叶绿酸-a甲酯为起始原料, 通过加成和氧化反应将其3-位上的乙烯基转化为羟乙基、溴乙基、二羟乙基、二溴乙基和溴羟乙基, 再经过二甲亚砜/乙酸酐或者高钌酸四丙基铵(TPAP)/N-甲基吗啉-N-氧化物所组成的混合氧化剂的氧化反应, 得到多种C(3)-多酮基取代的二氢卟吩衍生物. 其单羟基作为离去基团与不同的活泼亚甲基化合物经过重排过程, 得到相应的酮基取代的二氢卟吩衍生物. 所得新叶绿素衍生物的化学结构均经UV, IR, ¹H NMR及元素分析得以证实, 并对相应的反应提出可能的反应机理.     

Orientation effects in the nitration of the dithieno[b,d]pyridine N-oxides. Its dependence on acidity of the reaction medium

The nitration of three dithienopyridine-N-oxides was investigated. The regiochemistry of the reaction was dependent on the reaction conditions used. Under strongly acidic conditions the positional preference is similar for the N-oxides and free bases. However, under mildly acidic or neutral conditions a completely different substitution pattern was obtained. In the latter case those ring positions were substituted which are expected to be unfavored or forbidden in electrophilic substitution of the free bases. The structures of the nitro derivatives were proven by extensive use of ¹H and ¹³C nmr spectroscopy.     

Selective bromination of dihydroquinopimaric acid

The reaction of dihydroquinopimaric acid methyl ester with bromine was found to be chemo- and stereoselective. Regardless of the solvent (acetic acid, methanol, dioxane), bromination of the title compound with an equimolar amount of bromine occurs as electrophilic addition at the double C¹⁹=C²⁰ bond with formation of 14α-hydroxy- or 14α-methoxy-19R-bromo derivatives. The reaction with excess bromine (3 equiv) leads to the formation of 16S-bromo derivatives. The bromination process is accompanied by formation of epoxy bridge between the C¹⁴ and C²⁰ atoms. X-Ray analysis revealed two polymorphic modifications of (16S,19R)-16,19-dibromo-14β,20-epoxydihydroquinopimaric acid methyl ester.     

A convenient method for the synthesis of fluorinated α-cyanoacetates via phase-transfer catalysis

A simple and convenient method for the synthesis of fluorinated α-cyanoacetate derivatives has been developed by using electrophilic fluorination of allyl and benzyl substituted α-cyanoacetates with N-fluorobenzensulfonimide (NFSI) as electrophilic fluorinating agent via phase transfer catalysis. The reaction is transition metal free and carried out in aqueous and mild reaction conditions in the presence of readily available tetra-N-butylammonium iodide (TBAI) as phase-transfer catalyst.     

Carbonyl Activation by Selenium- and Tellurium-Based Chalcogen Bonding in a Michael Addition Reaction

In the last years the use of chalcogen bonding—the noncovalent interaction involving electrophilic chalcogen centers—in noncovalent organocatalysis has received increased interest, particularly regarding the use of intermolecular Lewis acids. Herein, we present the first use of tellurium-based catalysts for the activation of a carbonyl compound (and only the second such activation by chalcogen bonding in general). As benchmark reaction, the Michael-type addition between trans-crotonophenone and 1-methylindole (and its derivatives) was investigated in the presence of various catalyst candidates. Whereas non-chalcogen-bonding reference compounds were inactive, strong rate accelerations of up to 1000 could be achieved by bidentate triazolium-based chalcogen bond donors, with product yields of >90 % within 2 h of reaction time. Organotellurium derivatives were markedly more active than their selenium and sulphur analogues and non-coordinating counterions like BAr^F₄ provide the strongest dicationic catalysts.     

Generation of oxodiazonium ions 1. Synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides

Methods for the synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides, which include the reaction of 3-nitramino-4-(R-phenyl)furazans or their O-methyl derivatives with electrophilic agents, have been developed. Unsubstituted [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxide was synthesized from 3-nitramino-4-phenylfurazan upon the action of phosphorus anhydride or oleum, as well as from O-methyl derivative of 3-nitramino-4-phenylfurazan upon the action of H₂SO₄, MeSO₃H, CF₃CO₂H and BF₃·Et₂O, while 6-, 7-, 8-, and 9-nitro-substituted [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides — from the corresponding 3-nitramino-4-(nitrophenyl)furazans upon the action of the H₂SO₄-HNO₃ nitrating mixture. A suggestion has been made that an oxodiazonium ion is formed in these reactions from nitramines or their O-methyl derivatives upon the action of electrophilic agents, which is further involved into the intra-molecular reaction of electrophilic aromatic substitution (S _EAr) with the aryl group. The structure of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-N-oxides was confirmed by ¹H, ¹³C, and ¹⁴N NMR spectra. Theoretical studies by the B3LYP/6-311G(d,p) method of combined molecular system (O-methylated 3-nitramino-4-phenylfurazan + [H₃SO₄]⁺) resulted in calculation of thermodynamic parameters of the sequence of cascade elementary reactions leading to the formation of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxide.     

Kinetische Untersuchungen über die Silicium—Aryl-Spaltung mit Bromwasserstoff

Rate constants of the cleavage reaction of silicon aryl linkages with HBr were estimated for various aryl derivatives by means of NMR. A row of substituents was obtained, dependent on the cleavage rates. Correlation with theHammett function shows the electrophilic character of the reaction. The different cleavage rates give the possibility for specific cleavages of aryl groups from silanes.

     

H6P2W18O62: A green and reusable catalyst for the synthesis of 3,3-diaryloxindole derivatives in water

An efficient and improved procedure for the synthesis of oxindoles derivatives is developed via the electrophilic substitution reaction of indoles with various isatins in the presence of a Wells–Dawson tungsten heteropolyacid in water.     

Synthesis,Structure, and Transformations of New Endic Anhydride Derivatives

4-Azatricyclo[5.2.1.02,6]dec-8-ene and its N-phenyl derivative were synthesized by reaction of endic anhydride with amines, transformation of the amido acids thus obtained to imides, and subsequent reduction of the latter with lithium aluminum hydride. The unsubstituted tricyclic amine was brought into reactions with electrophilic reagents: p-toluenesulfonyl chloride, p-toluoyl chloride, m-tolyl isocyanate, phenyl isothiocyanate, and endic anhydride to obtain a number of new derivatives; also, the corresponding salt with 1-adamantanecarboxylic acid was isolated. N-(p-Tolylsulfonyl)- and N-(m-tolylcarbamoyl)-4-azatricyclo-[5.2.1.02,6]dec-8-enes were oxidized to the corresponding 8,9-epoxy derivatives with monoperoxyphthalic acid. The structure of the products was confirmed by the data of IR, ¹H and ¹³C NMR, and mass spectra. The molecular structures of N-(p-iodophenyl)bicyclo[2.2.1]hept-2-ene-endo-5,endo-6-dicarboximide and N-phenyl-4-azatricyclo[5.2.1.02,6]dec-8-ene were established by X-ray analysis.     

Selective Synthesis of Cyclic Nitroene-Sulfonamides from Aliphatic Sulfamides and NOBF4

Described herein is the development of a desaturation and N-β-nitration reaction of cyclic amides, which is achieved by a selective hydrogen atom transfer (HAT)/oxidative desaturation/electrophilic nitration process. In this procedure, di-tert-butyl peroxide (DTBP) acted both as the oxidant and HAT reagent, and electrophilic NOBF₄ as nitration source. Notably, the application of produced cyclic nitroene-sulfonamides was showcased by their efficient transformations into 3-piperidones and poly-substituted piperidine derivatives.     

Reactivity of 2‐substituted imidazo[1,2‐b]pyridazines: Preparation of 3‐nitro,nitroso and chloro derivatives

The synthesis of 2‐substitutedimidazo[1,2‐b]pyridazines and their reactivity towards electrophilic substitutions are reported. The nitration was shown to be very dependent on the nature of the 2 substituent. Nitrosation using sodium nitrite in acetic acid media as a general method failed in all cases whereas chlorination was observed in warm hydrochloric acid. In order to ascertain the structure of some chloro derivatives, chlorination using N‐chlorosuccinimide was also reported. Depending of the nature of the substituent, the reaction occurred at the C‐3 imidazolic position and/or at the substituent on position 2. The 3‐nitroso‐2‐phenyl derivative was finally obtained using an alternative synthetic pathway by direct condensation of 3‐amino‐6‐chloropyridazine to ω‐chloro‐ω‐nitrosoacetophenone. The structural determinations were ascertained using high field ^lH and ¹³C‐NMR.