Study of Intramolecular Cyclization of N-styryl-oxo-cinnamides (Ⅱ)

lnthepreviouspaper',wereportedtheintramolecularcyclizationsofamide4anditscis-eneisomerinanattempttosynthesizehomoclausenamideandzetaclausenamide2.Inordertostudytherelationshipbetweenthestereochemistryandtheilltramolecularcyclizationofthisseriesofcompounds,theamides5(cis-oxirane,trans-ene)and8(cis-oxirane,cis-ene)wereprepared,andtheirintramolecularcyclizationswerereportedinthispaper.Theamide5withm.p.152.O-l54.O"CwasobtainedfromDarzen'scondensationofcompound3withPhCHOinMeOHatl5-2OoCwithMeO…     

Synthesis and Intramolecular Cyclization of ω-Haloalkyl Dithiophosporus Acid Esters

y -Haloalkyl dithiophosphorus acid esters undergo the thermal rearrangement resulting in the corresponding 2-oxo-1,3,2-dithiaphosphacyclanes.     

Electrophilic Cyclization of Dimethyl(ω-phenylaminoalkyl)alkenylsilanes

Unsaturated organosilicon amines [CH₂ = CH(CH₂) _n ]Me₂Si[(CH₂) _m NHPh] at the action of Hg(OAc)₂ in THF solution transform to corresponding heterocycles. Regioselectivity of this intramolecular electrophilic heterocyclization is defined by the position of double bond relatively to the silicon atom. This is caused by -effect of the silyl group.     

Synthesis of 1,3-Diaryl-2-methoxyindenes by Hydriodic Acid–Catalyzed Cyclization of Aryl[2-(1-aryl-2-methoxyvinyl)phenyl]methanols

An efficient two-step method for the synthesis of 1,3-diaryl-2-methoxyindenes from 1-(1-aryl-2-methoxyvinyl)-2-bromobenzenes has been developed. Thus, the reaction of 2-(1-aryl-2-methoxyvinyl)phenyllithiums, generated in situ by halogen–lithium exchange between 1-(1-aryl-2-methoxyvinyl)-2-bromobenzenes and butyllithium, with aromatic aldehydes gives aryl[2-(1-aryl-2-methoxyvinyl)phenyl]methanols, which in turn are treated with a catalytic amount of concentrated hydriodic acid to afford the corresponding 1,3-diaryl-2-methoxyindenes in reasonable yields.     

Cyclization of 2-methoxy-6-(substituted benzyloxy)acetophenone hydrazones in the presence of polyphosphoric acid(PPA)

Cyclization of 2-methoxy-6-benzyloxy acetophenone hydrazone gave 3-methyl-4-meth-oxy indazole and 3-methyl-4-methoxy-7-benzyl indazole in the presence of polyphosphoric acid(PPA).The hydrazone was probably converted to 2-hydroxy-6-methoxy acetophenone hydra-zone and 2-hydroxy-3-benzyl-6-methoxy acetophenone hydrazone followed by cyclization to thecorresponding indazoles in acidic conditions.Cyelization of 2-methoxy-6-(halo or alkyl or arylbenzyloxy)acetophenone hydrazones gave similar products.Cyclization of 2-methoxy-6-(p-nitrobenzyloxy)acetophenone hydrazone gave 2-(p-nitrophenyl)-3-methyl-4-methoxy benzo-furan and 3-methyl-4-methoxy indazole while 2-methoxy-6-(m-nitrobenzyloxy)acetophenonehydrazone gave 3-methyl-4-methoxy indazole,3-methyl-4-methoxy-7-(m-nitrophenyl)indazole and3-methyl-4-(m-nitrobenzyloxy)indazole.     

Diastereoselective Synthesis of Rotationally Restricted Chiral Phenylpyridines via Intramolecular Cascade Cyclization of N-Acyliminium Ions Containing α-Amino Acid Residues

A series of chiral phenylpyridines possessing a fused chiral bridge were synthesized diastereoselectively via cascade cyclizations, where N-acyliminium ions including an enantiopure α-amino acid residue were involved. The absolute configuration of the synthesized phenylpyridines was identified unambiguously by using nuclear Overhauser effect difference and circular dichroism (CD) measurements on the basis of literature methods.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications^® for the following free supplemental resources: Full experimental and spectral details.]     

Study on the Intramolecular Cyclization through Opening of Epoxide Ⅳ. Cyclization of N-Methyl-N-benzoylmethylene β-Methyl-a, β- epoxypropionamide in Aprotic and Protic Solvents

Intramolecular cyclization of β -methyl substituted epoxide under aprotics （e.g. LDA in benzene） and protic conditions （e.g. LiOH in MeOH/H2O）both gave a mixture of β-,γ-, δ- and ε-lactam but in different ratio.     

Preparation of 1-[ω-(1,4,5,6-Tetrahydropyrimidin-2-Yl)Alkyl]Thymines

One-stage preparation of 1-[ω-(1,4,5,6-tetrahydropyrimidin-2-yl)alkyl]-thymines from 1-(ω-cyanoalkyl)thymines and a 1:1-mixture of 1,3-diaminopropane and ethanol saturated with hydrogen sulfide is described. 1-(2-Cyanoethyl)-thymine gave a facile reversal of the Michael reaction to thymine under the conditions used. The reaction of 1,3-bis(3-cyanobenzyl)thymine with the above reagent produced 1,3-bis[3-(1,4,5,6-tetrahydropyrimidin-2-yl)benzyl]thymine.     

A New Synthesis of 1-(ω-Haloalkyl)-Imidazoles

Inconnechonwith0urreeenteffortStowardsthesynthesis0fartificialreceptorsandenzymescontalninginddazoles",itwasnecessarytoprepareaclassofl-(orhaloalkyl)-inddazolesassyntheticpreeursors.The0nlyreportinliteratureislindtedforthepreparationofl-(2-bromoethyl)inddazolebyreactingimidazolefirstwithethylenecarbonate,thenwiththionylbr0nddet0givea24.5%yield'.Therearenogeneralpreparativemethodsforthesecompounds.RecenUy,HorvathreportedasimPlemethodf0rthepreparationofl-substitutedinddazolesfromaHoffmann-type…     

Cyclization of N-(2,4,6-trimethylphenyl)-β-alanines

Reaction of 2,4,6-trimethylaniline with acrylic and itaconic acids gives the corresponding N-substituted =alanines which can be converted to derivatives of tetrahydropyridone, dihydropyrimidinedione, and 4-carboxy-2-pyrrolidinone. Bromination of the aromatic substituent in the synthesized heterocycles has been carried out.Kaunas Technological University, Kaunas 3028, Lithuania Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 951–954, July, 2000     

Intramolecular allylboration of γ-(ω-formylalkoxy)allylboronates for syntheses of trans- or cis-2-(ethenyl)tetrahydropyran-3-ol and 2-(ethenyl)oxepan-3-ol

3-Alkoxy-1-alkynes 4 were hydroborated with pinacolborane (HBpin) to give 3-alkoxy-1-alkenylboronates 5. The latter gave (E)-3-alkoxyallylboronates (8: (E)-(MeO)₂CHCH₂(CH₂)_nCH₂OCHCHCH₂Bpin, n=1-3) when they were subjected to iridium-catalyzed isomerization of the double bond. The corresponding (Z)-isomers 10 were synthesized by nickel-catalyzed isomerization of 5. Both allylboronates underwent intramolecular allylboration leading to the formation of trans-2-(ethenyl)tetrahydropyran-3-ol or 2-(ethenyl)oxepan-3-ol from 8 and the corresponding cis-isomers from 10 in the presence of Yb(OTf)₃ (20 mol%) in aqueous acetonitrile at 90°C.     

Study on the Intramolecular Cyclization through Openmg of Epoxide IV. Cyclization of N-Methyl-N-benzoylmethylene β-Methyl-α, β- epoxypropionamide in Aprotic and Protic Solvents

Intramolecular cyclization of β -methyl substituted epoxide under aprotics (e.g. LDA in benzene) and protic conditions (e.g. LiOH in MeOH/H2O)both gave a mixture of β-, γ-, δ- and ε-lactam but in different ratio.     

Intramolecular [2 + 2] photocycloaddition. 2. Mechanism of intramolecular photocyclization of α,ω-bis(p-vinylphenyl)alkanes

From the photophysical measurements of the title reaction, the formation of cyclophanes is concluded to be facilitated by high microscopic concentration of styrene moieties and depressed by strain loaded at the transition state.     

Cyclization of 1-(4,4-diethoxybutyl)-3-aryl(thio)ureas to 2-arylpyrrolidines and 2,3´-bipyrrole derivatives

A reaction of 1-(4,4-diethoxybutyl)-3-phenylthiourea with resorcinol, 2-methylresorcinol, pyrogallol, and hydroquinone in chloroform in the presence of trifluoroacetic acid leads to 2-aryl-1-(N-phenylcarbamothioyl)pyrrolidines. 1-(4,4-Diethoxybutyl)-3-arylureas and 1-(4,4diethoxybutyl)-3-arylthioureas in the presence of an acid catalyst undergo intramolecular cyclization and dimerization with the formation of 1,1´-bis(N-arylcarbamo(thio)yl)-2,3´-bipyrrole derivatives.     

Total Synthesis of (-)-Baimuxifuranic Acid

ThenatieChenmanginclha,oneofthemoStbeandexpensivCherbaldrugSin~tionalChjnsemdednesisthewoodypartofAquIIarasinensisW.)Gilg.,whoseVofatileoilseforitaIUUnberofinterestinbiologicalandphannacologicalactivities,suchasanestheha,muscularrelaxationandanalgesta'.ReCentiyYanetaI2isolated(-)taim~cacid(1)frOmtheVOboleoilofChenAlang,anddeennineditSStIUCtUrbySpeCtrscoPicmethodandred~1toaknowncornPOunisobaimndnolCoInPOun1isthefirStcarboxylicacidwithdihydragarohanskeletonisolatedfromnisources.He…     

A Practical Synthesis of (S)-(+)-2-(6-methoxyl-2-naphthyl) propionic Acid

a-Arylpropionic acids are an important class of non-steroidal anti-inflammatory agents1,2. The therapeutic efficacy of this class of drugs is well demonstrated by the introduction and extensive use of more than a dozen compounds exemplified by ibuprofen, naproxen, ketoprofen and flurbiprofen etc. However, in recent years the use of enantiomerical pure drugs in chemotherapy is becoming almost mandatory for enhancing specificity of drug action and reducing the toxicity. This awareness led to …     

Synthesis of α-(perfluoroalkyl)-ω-(trialkylsilyl)alkanols

The synthesis of alkanols of the general formula R₃Si(CH₂)_nCH(OH)R_F (n = 1–3) is elaborated and their behavior under GC-MS is studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1516-1519, June, 1996.     

Vinyl Ethers Containing an Epoxy Group: XXI. Synthesis and Acid-Catalyzed Cyclization of 1-[ω-(Vinyloxy)alkoxy]-3-(2-propynyloxy)-2-propanols- A Simple Route to 2-Propynyloxymethyl-Substituted Cyclic Polyethers

Base-catalyzed reaction of 2-[-(vinyloxy)alkoxy]methyloxiranes with 2-propynyl alcohol (3 wt % of t-BuOK, 60-85°C, 3-12 h) afforded first reperesentatives of the 1-[-(vinyloxy)alkoxy]-3-(2-propynyloxy)-2-propanol series in up to 99% yield. Treatment of 1-[2-(vinyloxy)ethoxy]- and 1-[2-(vinyloxy)ethoxyethoxy]-3-(2-propynyloxy)-2-propanols with trifluoroacetic acid (0.5 wt. %) in dry diethyl ether resulted in cyclization with formation of up to 96% of (2-methyl-1,3,6-trioxocan-4-yl)methyl- and (2-methyl-1,3,6,9-tetraoxacycloundecan-4-yl)methyl 2-propynyl ethers.     

Synthesis of 8-(ω-Chloroalkyl)-dipyrrinones

Dipyrrinones,typically brightyellow compounds with a long axis- polarizedπ- π* excita-tion in the1 4 π- electron- conjugated chromophore,such as xanthobilirubic acid methyl ester(XBRMe) ,are useful building blocks for the syntheses of biologically important tetrapyrrolepigments such as bilirubin(the yellow pigmentof jaundice) [1 ],and they have been extensivelyused as model dipyrrole pigments for the spectroscopic and the photochemical studies of linertetrapyrroles such as bilirubin and bil…