Lactam acetals

Derivatives of pyrrolo-, pyrido-, and azepino[2,3-b]quinolones were synthesized by condensation of N-methylbutyro-, N-methylvalero-, and N-methylcaprolactam diethyl acetals with ethyl anthranilate. The corresponding ethoxy derivatives were obtained by reaction of these compounds with triethyloxonium tetrafluoroborate, and condensed 4-chloroquinolines were synthesized with POCl₃.See [1] for communication IX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 670–674, May, 1974.     

Lactam acetals

It is shown in the case of the reaction of N-methylbutyro-, N-methylvalero-, and N-methylcaprolactam diethylacetals with benzyl cyanide that the five-membered acetal is the most reactive in the reaction with compounds having an active methylene link. 1-Methyl-3-(Ωphenyl-Ω-benzoxymethylene)-2-pyrrolidone is primarily formed in the reaction of N-methyl-2-pyrrolidone diethylacetal with C₆H₅COCl. The reaction of N-methylcaprolactam diethylacetal with acrylonitrile gives a mixture of N-methylcaprolactam, 1-methyl-2-ethoxy-3-(Β-cyanoethyl)-4, 5,6,7-tetrahydroazepine, and 2-methyl-1,9-dehydro-9-cyano-2-azabicyclo-[5.2.0] nonane.     

Kinetic regularities of the reaction of dimethyldioxirane with cyclic acetals

Kinetic regularities of the reactions of dimethyldioxirane (1) with 1,3-dioxolane, 2-propyl-1,3-dioxolane, 2-i-propyl-1,3-dioxolane, 2-phenyl-1,3-dioxolane, and 2,2-pentame-thylene-1,3-dioxolane (RH) in acetone have been studied spectrophotometrically in the temperature range from 15 to 48°C. The reaction rate d[1] /dt=k[1]·[RH] does not depend on the oxygen concentration in the reaction mixture. The activation parameters in the reaction with 1,3-dioxolane have been determined: lgk=(5.13±0.6)−(10.07±0.82)/Q, where Q=2,303 RT kcal/mol.     

Enantioselective addition of a chiral thiazolidinethione-derived titanium enolate to acetals

[reaction: see text] High stereoselectivities (up to 98% de) have been achieved for the Lewis acid-mediated cross-coupling reaction of dimethyl acetals to a chiral 1,3-thiazolidine-2-thione-derived titanium enolate. The reaction affords enantiopure anti alpha-methyl-beta-alkoxy carbonyl compounds in a wide range of acetals.     

Reaction of resorcinol and its derivatives with urea acetals

Reaction of 2-methylresorcinol and pyrogallol with urea acetals of various structures was studied. Depending on the structure of the acetal used, reaction was established to result in eiter calix[4]resorcinols containing urea fragment or in imidazolidin-2-one derivatives.     

Amide acetals in the synthesis of pyridothienopyrimidines

Methyl 3-amino-4-arylaminothieno[2,3-b]pyridine-2-carboxylates containing various substituents in the benzene ring were synthesized by the Thorpe-Ziegler reaction of 4-arylamino-2-chloropyridine-3-carbonitriles with methyl thioglycolates. The influence of the substituent in the benzene ring, acetal structure, the solvent and the process temperature on the reactions of obtained compounds with amide acetals was studied. It was established that reactions with dimethylacetamide dimethylacetal in toluene smoothly results in amidine derivatives, viz., methyl 4-arylamino-3-[1-(dimethylamino)ethylidene]aminothieno[2,3-b]pyridine-2-carboxylates, regardless of the substituent in the benzene ring. Analogous reaction of p-fluoroderivative with dimethylacetamide dimethylacetal in refluxing anhydrous ethanol leads to intramolecular cyclocondensation to produce substituted pyridothienopyrimidines, viz., 5H-1-thia-3,5,8-triazaacenaphthenes, in good yields. Amidine derivatives were the major products in the case of the coupling of aminothienopyridines with dimethylformamide dimethylacetal under the same conditions. A new approach to the synthesis of substituted pyridothienopyrimidines, viz., 3H-1-thia-3,5,8-triazaacenaphthylenes, based on the prolonged heating of methyl 4-arylamino-3-[1-(dimethylamino)ethylidene]aminothieno[2,3-b]pyridine-2-carboxylates in the excess of acetic anhydride was elaborated. Putative mechanisms of the processes concerned are given.     

GaCl3-catalyzed insertion of isocyanides into a C-O bond in cyclic ketals and acetals

The reaction of cyclic ketals or acetals with 2,6-dibromophenylisocyanide in the presence of a catalytic amount of GaCl(3) results in the insertion of isocyanide into the carbon-oxygen bond of cyclic ketals and acetals. [reaction: see text]     

Quinoxalino[2,3-c]cinnolines and their 5-N-oxide: alkoxylation of methyl-substituted quinoxalino[2,3-c]cinnolines to acetals and orthoesters

We report the alkoxylation of methyl-substituted quinoxalino[2,3-c]cinnolines to give acetals and orthoesters in high yields. Routes to the precursors of this alkoxylation reaction as well as other quinoxalino[2,3-c]cinnoline and their 5-oxide derivatives are reported. Most of these quinoxalino[2,3-c]cinnolines were prepared by cyclization of the corresponding 2-amino-3-(2-nitrophenyl)quinoxaline, which, in turn, result from an unusual Beirut reaction from benzofurazan oxides plus 2-nitrobenzylcyanides. Mechanistic explanations for these intriguing reactions are presented.     

Use of an aminosilyllithium for the diastereoselective synthesis of diphenyl oxasilacyclopentane acetals and polyols

[reaction: see text] The conjugate addition reaction of a stable, in situ generated silyllithium gives a beta-hydroxysilyl ester with high diastereoselectivity. Conversion of the beta-hydroxysilyl ester to a beta-fluorosilyl ester affords the precursor to the oxasilacyclopentane acetal in high yields under mild conditions. A hydride reduction and subsequent intramolecular silylation lead to the acetal in excellent yields. Finally, highly selective nucleophilic substitution affords oxasilacyclopentanes, which undergo a mild oxidation to afford 1,3-trans diols with high selectivity.     

Lactam and acid amide acetals 68. 1-Cyanomethyl-2-pyrrolidone diethylacetal in the synthesis of 7,8-trimethylenepurine derivatives

1-Cyanomethyl-2-cyaniminopyrrolidine was synthesized by the reaction of 1-cyanomethyl-2-pyrrolidone diethylacetal with cyanamide. The product undergoes Thorpe—Ziegler cyclization under the influence of sodium ethoxide to give 2-amino-3-cyano-5,6-dihydro-7H-pyrrolo[1,2-a]imidazole, from which 4-amino derivatives of pyrrolo[2,1-f]purine were synthesized.See [1] for Communication 67.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 754–758, June, 1991.     

[1,2]-Wittig rearrangement of acetals. Part 2: The influence of reaction conditions

Acetals of seven alcohols with (+)-camphor derived enantiomerically pure 7,8,8-trimethyl-4,7-methanobenzofuran-2-ol were subjected to different reaction conditions favorable for a [1,2]-Wittig rearrangement. Results with regard to conversion, yield and stereochemical course depending on the reaction conditions are discussed.     

Lactam acetals

The diethyl acetal of N-methylpiperidin-2-one has been synthesized and its reactions with compounds having active CH₂ and CH₃ groups have been studied. In the reaction of diethyl acetal of N-methylpiperidin-2-one with malonic ester, in addition to the condensation product, ethylmalonic ester is formed. The reaction of the acetal with benzoic acid leads to O-alkylation and the formation of ethyl benzoate.For communication IV, see [2].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 954–957, July, 1973.     

Pd(II)-catalyzed conversion of styrene derivatives to acetals: impact of (-)-sparteine on regioselectivity

[reaction: see text] Pd[(-)-sparteine]Cl(2) catalyzes the formation of dialkyl acetals from styrene derivatives with Markovnikov regioselectivity. The substrate scope of this reaction has been investigated, and initial mechanistic studies indicate that the reaction proceeds through an enol ether intermediate and a Pd-hydride.     

Acetals of lactams and acid amides. 33. Reaction of secondary enamino amides with amide acetals and synthesis of condensed pyrimidines

Condensed pyrimidines were synthesized by the reaction of dimethylformamide and dimethylacetamide diethylacetals with secondary enamino amides. It is shown that the piperido[1,2-c]pyrimidine derivative undergoes rearrangement to a 1,6-naphthyridine derivative under mild conditions.See [1] for communication 32.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1120–1124, August, 1980.     

Lactams of acetals and acid amides, 45. Synthesis of condensed 2-pyridones from activated amides,lactams, and lactones

By reaction of lactim ethers with N-substituted cyanoacetamides, the corresponding enaminoamides were obtained, cyclization of which by dimethylformamide acetal gave derivatives of pyrrolo[3,2-c]pyridine, 1,6-naphthyridine, and pyrido[4,3-b]azepine, having a substituent at the nitrogen atom of the pyridone ring. N-substituted furo[3,2-c]pyridines were synthesized from the diethyl acetals of butyrolactone and 3-(dimethylaminomethylene)butyrolactone and dimethylformamide acetal.For communication 44, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 929–932, July, 1985.     

Efficient one-step aldol-type reaction of ketones with acetals and ketals mediated by dibutylboron triflate/diisopropylethyl amine

one-step Mukaiyama aldol type reaction [reaction: see text] A highly efficient one-step Mukaiyama aldol-type reaction has been developed for the synthesis of beta-alkoxy carbonyl compounds starting from ketones and acetals/ketals. The reaction is mediated by a combination of Bu(2)BOTf and i-Pr(2)NEt affording the products in high yields. Formation of the two possible diastereoisomers of the beta-alkoxy ketones from the chiral acetals shows that the condensation takes place by an S(N)1 mechanism, involving prior opening of the acetal to an oxonium ion.     

O-Directed free-radical hydrostannations of propargyl ethers, acetals, and alcohols with Ph3SnH and Et3B

[reaction: see text] The O-directed hydrostannation of various propargyloxy substrates is reported with Ph(3)SnH/Et(3)B.     

Enantioselective conjugate addition of silylketene acetals to beta-enamidomalonates. Synthesis of beta-amino acid derivatives

[reaction: see text] Conjugate addition of silylketene acetals or enolsilanes to enamidomalonates proceeds with excellent chemical efficiency and good selectivity using Cu(OTf)2 and a chiral bisoxazoline. The effect of the Lewis acid, ligand, the N-acyl substituent, and the nucleophile on yield and selectivity for the addition product have been evaluated.     

1-substituted beta-carbolines by a Pictet-Spengler cyclization with thioortho esters and carbon-carbon bond formation via N-sulfonyl iminium ions generated from N,S-sulfonyl acetals

The reaction of N-tosyltryptamines with thioortho esters, leading to 1-thiosubstituted tetrahydro-beta-carbolines under modified Pictet-Spengler conditions, is described. The 1-heterosubstituted beta-carbolines furnished 1-substituted beta-carbolines upon reaction with Grignard reagents and silyl derivatives under Lewis acid promotion. [reaction: see text]     

Metal-catalyzed regioselective oxy-functionalization of internal alkynes: an entry into ketones, acetals, and spiroketals

[reaction: see text] Platinum(II) and an unusual cationic gold(I) complex were identified as mild catalysts for the room temperature cycloisomerization or tandem hydroalkoxylation/acetal formation of unactivated internal alkynols. Under the appropriate conditions, 5-endo, 5-exo, 6-endo, and 6-exo cycloisomerization modes are all available.