Total Synthesis of Gracilamine

The total synthesis of gracilamine, a pentacyclic Amaryllidaceae alkaloid, was achieved from simple building blocks. The synthesis features a mild photo‐Nazarov reaction, intramolecular 1,4‐addition, and an intramolecular Mannich reaction. This approach not only confirms the C6 stereochemistry of natural gracilamine, and also provides a novel solution to prepare its derivatives and structurally related natural products.     

Aminomethylation of 6-methyl-1-(thietan-3-yl)pyrimidine-2,4(1H,3H)-dione

Mannich reactions of 6-methyl-1-(thietan-3-yl)pyrimidine-2,4(1H,3H)-dione with formaldehyde and morpholine, piperidine, N-methylpiperazine, and diethylamine gave the corresponding 5-aminomethylsubstituted pyrimidine derivatives. The title compound reacted with excess piperazine to form 3,5-bis-(piperazin-1-yl) derivative, while its reaction with an equimolar amount of piperazine afforded 5,5′-(piperazin-1,4-diylbismethylene)bis[6-methyl-1-(thietan-3-yl)pyrimidine-2,4(1H,3H)-dione].     

A simple and convenient method for synthesis of new aminonaphthoquinones derived from lawsone by catalytic multicomponent Mannich reaction

A clean, efficient and facile one-pot protocol was developed for the synthesis of a series of new aminonaphthoquinones derived from 2-hydroxy-1,4-naphthoquinone (lawsone) by three-component Mannich reaction using catalytic amount of p-TsOH in CH₃CN, at room temperature. At the present work, we improved the yield and significantly reduced the reaction time for several Mannich reactions with different amine and aromatic aldehydes using a non-expensive, mild catalyst and suitable solvent.     

The use of amino acids in the mannich reaction

Amino acids have been found to participate as the amine component in the Mannich reaction with both ketones and phenols. The phenolic Mannich bases may be cyclized with sulfuric acid to 1,2-dihydro-4(3/H)isoquinolones. In the presence of thionyl chloride the same Mannich bases undergo lactonization to benz[f]-1,4-oxazepin-4(3H)ones.     

Synthesis of Isatin and 5-Bromoisatin Derivatives

New N-derivatives of isatin were synthesized by treating ethyl chloroacetate, N-(2-chloroethyl)morpholine, and 1,4-di(chloromethyl)benzene with isatin sodium salt. N-Derivatives of isatin and 5-bromoisatin were also prepared by Mannich reaction.     

高对映选择性有机催化的七元环状亚胺二苯并1,4-氧氮杂卓和丙酮的直接Mannich反应(英文)

用脯氨酸作为催化剂,研究了各种取代的二苯并1,4-氧氮杂卓衍生物类七元环状亚胺和丙酮的直接Mannich反应,该反应能高对映选择得到一系列旋光活性的含有β羰基的七元环状氮杂环化合物(93%–98%ee).用丁酮作为Mannich给体时,能得到专一的区域选择性和96%–97%ee的产物.进一步通过X射线单晶衍射分析其中一个产物的衍生物,确定了产物手性中心绝对构型为R,其它同类型产物绝对构型随后通过化学类比方法推断确认.     

A tandem Diels–Alder/Mannich approach to the synthesis of AE and ABE ring analogues of Delphinium alkaloids

The one-pot TiCl₄ catalysed Diels–Alder/Mannich reaction of α-cyanoaminoacrylates with 2-silyloxy-1,4-butadienes gives 6-keto-3-azabicyclo[3.3.1]nonane-1-carboxylates. Reduction of the ketone and alkylation of the resultant alcohol gives 6-alkoxy-3-azabicyclo[3.3.1]nonanes mimicking the AE rings of a number of Delphinium and Aconitum alkaloids, with the same stereochemistry as the natural products.     

Synthesis, Structure, and Growth-Regulating Activity of 1-(6,9-Dimethyl-1,4-dioxa-8-azaspiro[4,5]dec-8-ylmethyl)-1H-pyridin-2-one

1-(6,9-Dimethyl-1,4-dioxa-8-azaspiro[4,5]dec-8-ylmethyl)-1H-pyridin-2-one was prepared by the Mannich reaction from 6,9-dimethyl-1,4-dioxa-8-azaspiro[4,5]decane, formaldehyde, and pyridin-2-one in alcohol. Its structure was proved by NMR spectroscopy. This compound exhibits a growth-regulating activity.     

Asymmetric Traceless Petasis Borono‐Mannich Reactions of Enals: Reductive Transposition of Allylic Diazenes

The traceless Petasis borono‐Mannich reaction of enals, sulfonylhydrazines, and allylboronates, catalyzed by chiral biphenols, results in an asymmetric reductive transposition of the in situ generated allylic diazene. Acyclic 1,4‐diene products bearing either alkyl‐ or aryl‐substituted benzylic stereocenters are afforded in excellent yields and enantiomeric ratios of up to 99:1. The use of crotylboronates in the reaction results in concomitant formation of two stereocenters in either a 1,4‐syn or anti relationship from the corresponding E ‐ or Z ‐crotylboronate used in the reaction. The use of β‐monosubstituted enals in the asymmetric traceless Petasis borono‐Mannich reaction of crotylboronates installs tertiary methyl‐bearing stereocenters in good yields and high enantioselectivities.     

双锂试剂与6, 6-二烷基富烯的反应-取代茂钛，锆有机化合物的合成

研究了双锂试剂与6, 6-二烷基富烯反应的立体、结构效应。1, 4-丁基二锂、1, 6-己基二锂同6, 6-二甲基、6-甲基-6-乙基、6-甲基-6-正丙基和6, 6-五甲基富烯发生加成反应。对苯基二锂与6, 6-二甲基、6-甲基-6-乙基、6-甲基-6-正丁基和6, 6-四甲基、五甲基、六甲基富烯均进行α-攫氢反应, 但使6-甲基-6-正丙基富烯还原偶联。1, 2, 3, 4-四苯基-1, 4-二锂丁二烯-1, 3同6-甲基-6-正丙基、6, 6-五甲基富烯发生α-攫氢反应。讨论了上述反应的机理。由上述形成的取代环戊二烯基阴离子同CpTiCl~3, (CpTiCl~2)~2O, TiCl~4和ZrCl~4反应, 制得亚甲基桥联和烯基茂钛、锆化合物。     

取代邻苯二酚Mannich反应研究I:

把3-[N,N-双(羧甲基)氨甲基]邻苯二酚和哌啶,吡咯,二乙胺,吗啉和哌嗪在加热可得到相应的5-取位Mannich碱.研究了Mannich反应的机理,理解了这一Mannich反应的定位是由于反应物的分子内氢键.但是在与亚胺基二乙酸反应时或3-吗啉甲基邻苯二酚与吗啉反应,得到正常的6-取代Mannich碱.     

New access to 4-phenyl-6H-pyrrolo[1,2-a]thieno[3,2-f]-[1,4]diazepines

Pyrrolo[1,2-a]thieno[3,2-f][1,4]diazepines were obtained in an original one step synthesis by treatment of imines 1 with paraformaldehyde in refluxing ethanol. The intermediate Mannich bases were also converted into the thienooxadiazocines 12 and the diazepine N-oxide 13 .     

Expedient synthesis of chiral 1,2- and 1,4-diamines: protecting group dependent regioselectivity in direct organocatalytic asymmetric Mannich reactions

[reaction: see text] Organocatalytic asymmetric Mannich reaction of protected amino ketones with imines in the presence of an L-proline-derived tetrazole catalyst afforded diamines with excellent yields and enantioselectivities of up to 99%. The amino ketone protecting group controlled the regioselectivity of the reaction providing access to chiral 1,2-diamines from azido ketones and 1,4-diamines from phthalimido ketones.     

Behavior of 2‐iminothiazolidin‐4‐one with different reagents

Annulations of 2‐imino‐4‐thiazolidinone ( 5 ) via cycloaddition followed by cyclocondensation reaction with 1,3‐diphenylpropenone ( 6 ), benzylidenemalonate, and 1,2‐bis(chloromethyl)benzene gave 7 , 19 and 20 , respectively. Reaction of 5 with suitable electrophiles (Mannich bases of arylalkanone), 1,4‐dichlorobenzene (diarylmethylation), and formylation afforded 8 / 9 , 21 / 22 , and 23 , respectively. J. Heterocyclic Chem., (2011).     

The Mannich reaction in the synthesis of N,S-containing heterocycles 11. Synthesis of 3,3′-(1,4-phenylene)-bis(8-aryl-6-oxo-3,4,7,8-tetrahydro-2H,6H-pyrido[2,1-b][1,3,5]thiadiazine-9-carbonitriles)

N-Methylmorpholinium 4-aryl-3-cyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates readily undergo the Mannich reaction with p-phenylenediamines and excess formaldehyde in the absence of a catalyst to form 3,3??-(1,4-phenylene)-bis(8-aryl-6-oxo-3,4,7,8-tetrahydro-2H,6H-pyrido[2,1-b][1,3,5]thiadiazine-9-carbonitriles) in moderate yields (24?C56%).     

An application of the mannich reaction using hydroxylamine and some of its derivatives. 6-Substituted-2,4-diamino-5,6,7,8-tetrahydropyrimido[4,5-dpyrimidines

Hydroxylamine and some of its O -substituted derivatives ( 2 ) have been used as the amine component in Mannich reactions with 2,4,6-triaminopyrimidine ( 1 ). The resulting 6-substituted tetrahydropyrimido[4,5-d]-pyrimidines ( 3 ) contain an N-0 bond linking the substituent to the ring. These results extend the utility of this modified Mannich reaction to otherwise inaccessible substituents. Reaction conditions, spectral data and certain limitations of the reaction are discussed.     

Synthesis of pyrrolo[2,1-c][1,4]benzoxazepines. 1. A novel heterocyclic ring system

The synthesis of a novel pyrrolo[2,1-c][1,4]benzoxazepine ring system (II) by a nucleophilic aromatic fluoride displacement-cyclization is described. Aminoalkyl derivatives were prepared by either the Mannich reaction, or Vilsmeier formylation to provide the 3-formyl derivative which was further elaborated.     

Mannich bases and methiodides of 6-(2-furyl)imidazo[2,1-b]thiazole and its substituted derivatives

The Mannich reaction in a number of 6-(2-furyl)-substituted imidazo[2,1-b]thiazoles is realized initially in the 5 position of the imidazothiazole system, whereas it is also realized in the 5 position of the furan ring in the presence of excess reagents if the latter position is not substituted. Iodomethylation occurs at the N₇ atom of imidazothiazole. The Mannich bases of 6-(5-nitro-2-furyl)imidazo[2,1-b]thiazole are iodomethylated only at the aminomethyl group. The pK_a values of the series of compounds were measured.     

Reactions of coordinated hydroxymethylphosphines with NH-functional amines: the phosphorus lone pair is crucial for the phosphorus Mannich reaction

Non-coordinated hydroxymethylphosphines react readily with primary and secondary amines by the phosphorus Mannich reaction. To determine if this reactivity can be used to synthesize phosphine macrocycles, trans-Fe(DHMPE)(2)Cl(2) (DHMPE = 1,2-bis(dihydroxymethylphosphino)ethane) was prepared and reacted with various amines. However, no phosphorus Mannich reactivity was observed. In order to understand why no reactions occurred, the Mannich reactivity of the borane-coordinated hydroxymethylphosphines DHMPE·2BH(3) and Ph(2)PCH(2)OH·BH(3) was investigated. These borane-coordinated phosphines also did not undergo the phosphorus Mannich reaction. These results suggest that the lone pair of electrons on the phosphorus atom is essential for the phosphorus Mannich reaction to occur, and therefore it is not possible to use this reaction in a templated synthesis of phosphine macrocycles. It is speculated that the mechanism of the phosphorus Mannich reaction may involve a methylenephosphonium intermediate, analogous to an iminium in the standard Mannich reaction. X-ray crystal structures of trans-Fe(DHMPE)(2)Cl(2) and DHMPE·2BH(3) are also presented. Both crystal structures display an extended hydrogen-bonding network in the solid state.     

Bissilyl enal: a useful linchpin for synthesis of functionalized vinylsilane species by anion relay chemistry

Bissilyl enal, prepared by a Mannich reaction of 3,3-bissilyl aldehyde with formaldehyde, has proven to be a useful linchpin in an efficient three-component coupling process. The reaction features a [1,4]-Brook rearrangement to generate the silylallyl anion, which adopts a predominant endo-orientation and can undergo addition to electrophiles in a regio- and stereoselective manner, giving various E-vinylsilane species in good yields.