Diels-alder reactions with 2-(Arylsulfinyl)-1,4-benzoquinones: effect of aryl substitution on reactivity, chemoselectivity, and pi-facial diastereoselectivity

Diels-Alder reactions of (SS)-2-(2'-methoxynaphthylsulfinyl)-1, 4-benzoquinone (1b), 2-(p-methoxyphenylsulfinyl)-1,4-benzoquinone (1c), and 2-(p-nitrophenylsulfinyl)-1,4-benzoquinone (1d) with cyclopentadiene are reported. These cycloadditions allowed the highly chemo- and stereoselective formation of both diastereoisomeric endo-adducts resulting from reaction on the unsubstituted double bond C(5)-C(6) of quinones working under thermal and Eu(fod)(3)- or BF(3).OEt(2)-catalyzed conditions. The synthesis of endo-adduct [4aS,5S,8R,8aR,SS]-9d resulting from cycloaddition on the substituted C(2)-C(3) double bond was achieved in a chemo- and diastereoselective way from quinone 1d in the presence of ZnBr(2). The reactivity and selectivity of the process proved to be dependent on the electron density of the arylsulfinyl group.     

Efficient trans-selectivity in the cyclocondensation of (S)-2-[2-(p-tolylsulfinyl)phenyl]acetaldehyde with activated dienes catalyzed by Yb(OTf)3

Reactions of (S)-2-[2-(p-tolylsulfinyl)phenyl]acetaldehyde 1 with Danishefsky's and related dienes took place in the presence of Yb(OTf)3 in a completely stereoselective manner, mediated by a remote sulfinyl group (1,5-asymmetric induction), to afford the corresponding 2,3-dihydro-4H-pyran-4-ones. These reactions followed a stepwise mechanism, as was corroborated by isolation of the corresponding intermediates, with a high level of trans-selectivity for 4-methyl-substituted dienes. Treatment of the adducts with Raney Ni provided concomitant cleavage of the C-S bond and reduction of the conjugated carbonyl grouping.     

The reaction of (N-isocyanimino)triphenylphosphorane with dialkyl acetylenedicarboxylates in the presence of 1,3-diphenyl-1,3-propanedione: a novel three-component reaction for the stereoselective synthesis of dialkyl (Z)-2-(5,7-diphenyl-1,3,4-oxadiazepin-2-yl)-2-butenedioates

Reactions of dialkyl acetylenedicarboxylates with (N-isocyanimino)triphenylphosphorane in the presence of 1,3-diphenyl-1,3-propanedione proceed smoothly at room temperature to afford dialkyl (Z)-2-(5,7-diphenyl-1,3,4-oxadiazepin-2-yl)-2-butenedioates in high yields. The stereochemistry of the final products were confirmed by single crystal X-ray structure determination. The reaction is completely stereoselective.     

Remote stereocontrol using (E)-6-hydroxy-4-methylhex-2-enyl(tri-n-butyl)stannane

Reactions of (E)-6-hydroxy-4-methylhex-2-enyl(tributyl)stannane (11) with aldehydes, when promoted by tin(IV) bromide, proceed with effective 1,5-stereocontrol to give (Z)-1,5-anti-5-methylhept-3-ene-1,7-diols (23), suitable precursors for the stereoselective synthesis of eight-membered lactones.     

Lithiation of 3-(Acylamino)-2-unsubstituted-, 3-(Acylamino)-2-ethyl-, and 3-(Acylamino)-2-propyl-4(3H)-quinazolinones: Convenient Syntheses of More Complex Quinazolinones(1)

3-(Pivaloylamino)- and 3-(acetylamino)-4(3H)-quinazolinones react with alkyllithium reagents to give 1,2-addition products in very good yields. Lithiation takes place with LDA and is regioselective at position 2. The lithium reagents thus obtained react with a variety of electrophiles to give the corresponding substituted derivatives in very good yields. Reactions of the lithium reagents with iodine give oxidatively dimerized cyclic structures. 3-(Pivaloylamino)- and 3-(acetylamino)-2-ethyl-4(3H)-quinazolinones and 3-(pivaloylamino)- and 3-(acetylamino)-2-propyl-4(3H)-quinazolinones are lithiated at the benzylic position with LDA. The lithium reagents so produced also react with a variety of electrophiles to give the corresponding 2-substituted-4(3H)-quinazolinone derivatives in very good yields. However, lithiation of 3-(acylamino)-2-(1-methylethyl)-4(3H)-quinazolinones was unsuccessful, as were lithiations of compounds having a diacetylamino group at position 3. The amide groups have been cleaved in good yield under basic or acidic conditions from some of the products to provide access to the free amino compounds.     

Reactions of 3-(Prop-2-enylidene)azetidin-2-ones with 4,5-Dihydro-3H-1,2,4-triazole-3,5-diones

The 3-(2-propenylidene)-β-lactams 1a–c react as semicyclic dienes with the dihydrotriazole-diones 2 in a stereoselective fashion leading to the cycloadducts 3 . The 3′,3′-disubstituted derivative 4 gives no [4 + 2]-cycloaddition products but forms the adducts 5 and 6 . Sterochemistry and reaction pathways are discussed.     

Synthesis of 5-Amino-1-aryl-4-(4-aryl-1,3-thiazol-2-yl)- 2,3-dihydro-1H-pyrrol-3-ones*

Reactions of 2-(4-aryl-1,3-thiazol-2-yl)-3-oxo-4-chlorobutyronitriles with primary aromatic amines result in nucleophilic substitution of the chlorine atom by amino group, followed by intramolecular addition of the secondary amino group to the cyano group. The products are 5-amino-1-aryl-4-(4-aryl-1,3-thiazol-2-yl)- 2,3-dihydro-1H-pyrrol-3-ones which are structurally related to the known antiischemic drugs.     

Synthesis of 1-(N-arylaminomethyl)-3-methyl-1,8-dihydrocycloheptapyrazol-8-ones

Reactions of 3-methyl-1,8-dihydrocycloheptapyrazol-8-one ( 2 ) with arylamines in the presence of formaldehyde gave 1-(N-arylaminomethyl)-3-methyl-1,8-dihydrocycloheptapyrazol-8-ones 5a-l in good yields. 1,3,5-Tris(phenyl- and 4-methoxyphenyl)hexahydro-1,3,5-triazines or bis(3-nitroanilino)methane, which were condensation products of arylamines and formaldehyde, also reacted with compound 2 to afford 5a,c,j , respectively.     

Synthesis of pyrimidino[4,5-b][1,5]benzodiazepin-2-ones and pyrimidino[1,6-a]benzimidazol-1-ones from 4-ethoxycarbonylamino-1H-1,5-benzodiazpine-3-carbonitrile via 4-(2-aminoanilino)pyrimidin-2(1H)-one-5-carbonitriles

Reactions of 4-ethoxycarbonylamino-1H-1,5-benzodiazepine-3-carbonitrile (2) with aliphatic primary amines gave 1-substituted 4-(2-aminoanilino)pyrimidin-2(1H)-one-5-carbonitriles 3. Analogous reactions of 2 with aromatic primary amines afforded 2-(2′-anilino-1′-cyanovinyl)benzimidazoles 5 and 6. Upon treatment with triethylamine, 3 underwent intramolecular cyclization to give 3-substituted 5-aminopyrimidino[4,5-b]-[1,5]benzodiazepin-2(3H,11H)-ones 8 . Heating of 3 with p-toluenesulfonic acid in ethanol gave 2-substituted pyrimidino[1,6-a]benzimidazol-1(2H)one-4-carbonitriles 9 . Reactions of 2 with hydrazines were also described. Mechanistic pathways are proposed to account for the products.     

Stereoselective syntheses of 4-hydroxy 4-substituted glutamic acids

The 4-hydroxy 4-substituted glutamic acid moiety is a common substructure of biologically important natural products such as monatin [(2S,4S)-2], lycoperdic acid (3), and dysiherbaine (4). To develop methodology for syntheses of these natural products, cycloadditions of nitrone 5 with 2-substituted 2-propen-1-ols 6 and 2-substituted acrylates 8 were investigated. Reactions of nitrone 5 with alcohols 6 in the presence of MgBr2OEt2 gave cycloadducts 7 in a highly stereoselective manner, whereas noncatalyzed reactions of 5 with acrylates 8 afforded adducts 9. Using the former reaction, syntheses of monatin [(2S,4S)-2], monatin derivative 18, and lycoperdic acid (3) were accomplished. The C4-epimer of monatin [(2S,4R)-2)] was also synthesized by employing the latter cycloaddition.     

Syntheses and structures of the arylaluminum chalcogenides (ArAlE)2 (Ar = 2-(NEt2CH2)-6-MeC6H3, E = Se; Ar = 2,6-(NEt2CH2)2C6H3, E = Se, Te)

Two intramolecular stabilized arylaluminum dihydrides, (2-(NEt2CH2)-6-MeC6H3)AlH2 (1) and (2,6-(NEt2CH2)2C6H3)AlH2 (2), were prepared by reducing the corresponding dichlorides with an excess of LiAlH4 in diethyl ether. Reactions of 1 and 2 with elemental selenium afforded the dimeric arylaluminum selenides [(2-(NEt2CH2)-6-MeC6H3)AlSe]2 (3) and [(2,6-(NEt2CH2)2C6H3)AlSe]2 (4). Reaction of 2 with metallic tellurium gave the dimeric arylaluminum telluride [(2,6-(NEt2CH2)2C6H3)AlTe]2 (5). The possible reaction pathway is discussed, and molecular structures determined by single-crystal X-ray analyses are presented for 3 and 5.     

Synthesis of Fluorine-Containing 2-(1-Aryl-4-oxo-1,4-dihydrocinnolin-3-yl)-2-oxoacetic Acids

Acid hydrolysis of ethyl 2-(1-aryl-5,6,7,8-tetrafluoro-4-oxo-1,4-dihydrocinnolin-3-yl)-2-oxoacetates gives 2-(1-aryl-5,6,7,8-tetrafluoro-4-oxo-1,4-dihydrocinnolin-3-yl)-2,2-dihydroxyacetic acids which undergo dehydration on heating in toluene to afford 2-(1-aryl-5,6,7,8-tetrafluoro-4-oxo-1,4-dihydrocinnolin-3-yl)-2-oxoacetic acids. Reactions of the latter with excess morpholine result in replacement of two fluorine atoms in positions 5 and 7 by the amine residues.     

Synthesen und Ringerweiterungsreaktionen von 2-(4-Hydroxyalkyl)-2-nitrocycloalkanonen

Syntheses and Ring-Enlargement Reactions of 2-(4-Hydroxyalkyl)-2-nitrocycloalkanones Syntheses of the title compounds were achieved by [Pd{P(C₆H₅)₃}₄]-catalyzed reaction of 2-nitrocycloalkanones 3 with vinyloxirane followed by catalytic hydrogenation. By another route, the known methyl 4-(1-nitro-2-oxocycloalkyl)butanoates 6 were reduced to the corresponding aldehydes 7 which by NaBH₄ reduction or methylation with (CH₃)₂Ti(i-Pr)₂ were transformed to the alcohols 5 and 8 , respectively (Saheme 1). Treatment of 5 and/or 8 with KH/THF under reflux gave, via a 7-membered intermediate, the nitrolactones 12 and oxolactones 13 (Scheme 3). Compared with similar reactions running via 5- or 6-membered intermediates (see 1 and 2 ), the yields are distinctly lower. The natural occurring 12-tridecanolid ( 14 ) was synthesized.     

2-Acyl(aroyl)-1,1,3,3-tetracyanopropenides: II. Synthesis of 2-[2-(alkylsulfanyl)-5-amino-2-aryl-4-cyano-2,3-dihydrofuran-3-ylidenepropanedinitriles by reaction with thiols

Reactions of 2-aroyl-1,1,3,3-tetracyanopropenides with thiols in acid medium led to the formation of the corresponding 2-alkylsulfanyl-substituted 2-(5-amino-2-aryl-4-cyano-2,3-dihydrofuran-3-ylidene)propanedinitriles.     

Synthesis of 1-[3-methyl-2(3H)-benzazolon-5- or 6-yl]-4-{4-[cis-2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl-methyl)-1,3-dioxolan-4-yl]methyleneoxyphenyl}piperazines

Reactions of 3-methyl-6-[4-(4-hydroxyphenyl)-1-piperazinyl]-2(3H)-benzoxazolone, 3-methyl-6-[4-(4-hydroxy-phenyl)-1-piperazinyl]-2(3H)-benzothiazolone and 1,3-dimethyl-5-[4-(4-hydroxyphenyl)-1-piperazinyl]-2(3H)-benzimidazolone with cis-{[2-(2,4-dichlorophenyl) -2-(1H-imidazol-1-ylmethyl)]-1,3-dioxolan-4-yl}methyl meth-anesulfonate in the presence of sodium hydride furnish the title compounds.     

Application of a new tandem isomerization-aldolization reaction of allylic alcohols to the synthesis of three diastereoisomers of (2R)-1,2-O-isopropylidene-4-methylpentane-1,2,3,5-tetraol

The tandem isomerization-aldolization reaction of (2R)-1,2-O-isopropylidene-4-penten-1,2,3-triol 3 and formaldehyde gives a mixture of two aldol products 2a and 2b. The stereoselective reduction of each compound by l-Selectride affords two diastereoisomers of (2R)-1,2-O-Isopropylidene-4-methylpentane-1,2,3,5-tetraol while a third diastereoisomer is obtained by stereoselective reduction with Me(4)NHB(OAc)(3).     

New synthesis of 4-(1-adamantyl)-2-aryl-1,3-thiazoles from 4-(1-adamantyl)-1,2,3-thiadiazole

Treatment of 4-(1-adamantyl)-1,2,3-thiadiazole with potassium tert-butoxide generated potassium 2-(1-adamantyl)ethynethiolate which reacted with aromatic carboxylic acid chlorides to give unstable S-[2-(1-adamantyl)ethynyl] arenecarbothioates whose acid hydrolysis afforded S-[2-(1-adamantyl)-2-oxoethyl] arenecarbothioates. The latter reacted with ammonium acetate in acetic acid yielding 4-(1-adamantyl)-2-aryl-1,3-thiadiazoles. Reactions of 4-(1-adamantyl)-2-(4-chloro-3-nitrophenyl)-1,3-thiadiazole with cyclic secondary amines gave the corresponding products of nucleophilic replacement of the chlorine atom in the aromatic ring.     

Synthesis of 2-(1,5,9-Triazabicyclo[7.3.1]tridec-10-en-5-yl)-4-methylthiobutanoic Acid Derivatives

Reactions of 1,3-bis(3-chloro-2-hydroxypropyl)uracil, 1,3-bis(3-chloro-2-hydroxypropyl)-6-methyluracil, 1,3-bis(3-chloro-2-hydroxypropyl)-5-hydroxy-6-methyluracil, and 1,3-bis(3-chloro-2-hydroxypropyl)-5-fluorouracil with 2-amino-4-methylthiobutanoic acid (methionine) were studied for the first time.     

Benzolactams. 4. Reaction of 3',4'- or 4',5'-dialkoxy-substituted 1-(2'-Bromobenzyl)-2-ethoxycarbonyl-1,2,3,4-tetrahydroisoquinolines with alkyllithium. 1,2 and 1,4 additions of alkyllithium to benzolactams

Treatment of 1-(2'-bromo-3',4'-dialkoxybenzyl)-1,2,3, 4-tetrahydroisoquinoline carbamates, 1a,c, with excess alkyllithium gave 8-oxoberbines, 2a,c, which were successively attacked in situ with another molecule of alkyllithium to give 1,2 and/or 1,4 addition products. A primary alkyllithium, such as MeLi or BuLi, gave a 1,2 addition product, 8-methyleneberbine 9a or 8-butylideneberbine 3a. t-BuLi preferred 1,4 addition, followed by elimination of the alkoxy group, to give 9-tert-butyl-8-oxoberbine 6a or 7c. s-BuLi gave a mixture of 1,2 and 1,4 addition products, 1-[2'-(2' '-methylbutyryl)benzyl]-1,2,3,4-tetrahydroisoquinoline 4a and 9-s-butyl-8-oxoberbine 5a. Similar treatments of carbamate 1b having no alkoxy group at its 3' position gave 1,2 addition products, 8-butylideneberbine 3b, 1-[2'-(2' '-methylbutyryl)benzyl]-1,2,3, 4-tetrahydroisoquinoline 4b, and 1-(2'-pivaloylbenzyl)-1,2,3, 4-tetrahydroisoquinoline 6b, in all cases. Reactions of 1a with s-BuMgCl and isoPrMgCl also gave the 1,4 adduct, 5a, and its 9-isoPr analogue, 12a. Treatment of 9a with excess NaBH(4) in AcOH gave (+/-)-coralydine (10b).     

Pd-catalyzed synthesis of 3-(diarylmethylene)-2-oxindoles and 3-(arylmethylene)-2-oxindoles

An efficient method for the stereoselective synthesis of 3-(diarylmethylene)-2-oxindoles and 3-(arylmethylene)-2-oxindoles via carbopalladation is described. In this approach, an Ugi-4-component reaction (4-CR) adduct was used as the starting material. A one-pot sequence involving intermolecular carbopalladation C-H activation/C-C bond formation efficiently afforded the oxindole derivatives.