Reaction Of 5c Research Articles

Synthesis of 2,5-Diaminopyrazine Derivatives via Dimerization of 2H-Azirin-3-amines

The 2-monosubstituted 2H-azirin-3-amine (5c) was prepared conveniently by subsequent treatment of N-methyl-N-phenylpropanamide in THF with LDA, diphenyl phosphorochloridate (DPPCl) , and sodium azide in DMF. In the absence of nucleophiles, the reaction of 5c in THF with BF 3 .OEt 2 at -78°C yields 2,5-dihydro-2,5-dimethyl-3,6-bis(N-methyl-N-phenylamino)pyrazinium tetrafluoroborate (11). Treatment of the latter with NaOH yields the corresponding 2,5-dihydropyrazine derivative (12), whereas dehydrogenation with DDQ leads to 2,5-dimethyl-3,6-bis(N-methyl-N-phenylamino)pyrazine (13). The structures of 12 and 13 were established by X-ray crystallography.

Synthesis and properties of alkaline metal complexes with new overcrowded β-diketiminato ligands

Enaminoimines TbtNHC(Me)CHC(Me)NAr ( 5, Tbt = 2,4,6-[CH(SiMe 3) 2] 3C 6H 2) bearing a Tbt group were synthesized by the two steps condensation of acetylacetone with bulky amines. Enaminoimines 5 were treated with n-BuLi to give the corresponding lithium β-diketiminates, [Li{TbtNHC(Me)CHC(Me)NAr}] ( 1). The X-ray structural analysis of [Li{TbtNC(Me)CHC(Me)NMes}] ( 1c, Mes = mesityl) revealed that it is a monomeric, solvent-free lithium β-diketiminate. The equilibrium between free 1c plus THF and THF-coordinated ( 1c · thf) was investigated in detail by the determination of the association constant ( K a) in C 6D 6 at 293 K and the Job’s plot. The heavier alkali metal complexes, sodium and potassium β-diketiminates ( 6c– 9c), were prepared by the two routes. THF-coordinated [M{TbtNC(Me)CHC(Me)NMes}(thf)] ( 6c: M = Na. 7c: M = K) were prepared by the reaction of 5c (Ar = Mes) with MH (M = Na, K). Solvent-free [M{TbtNC(Me)CHC(Me)NMes}] ( 8c: M = Na. 9c: M = K) were prepared by the reaction of 1c with t-BuOM (M = Na, K).

Synthesis of the monoterpene alkaloid bakankosin from secologanin

Reduction of secologanin 1a with sodium borohydride followed by acylation afforded 86% of sweroside tetraacetate 4 which was transformed to the 8-iodomethylester 5c by treatment with trimethylsilyliodide, hydrolysis and addition of diazomethane in 92% yield. Reaction of 5c with sodium azide gave 65% of the 8-azidomethylester 5d which was reduced with 1,3-propanedithiol to give bakankosin 2a after solvolysis in 80% yield.

Reactions of Haloarenes with Thiolate Anions in Tetraglyme: Competition between electron transfer and SNAr mechanisms

AbstractThe reaction of the bromo‐substituted naphthalene 1 with the alkanethiolate anions 2a–b and arenethiolate 2c in tetraglyme gave the corresponding 1‐naphythyl thio‐ethers 3a–c. Thio‐ethers 3a–c were oxidized to the corresponding sulfones 4a–c with m‐ chloroperoxybenzoic acid. The reaction of the dichloro‐substituted anthracene 5a with 2b gave the disubstutution product 6a. The reaction of 9‐bromoanthracene 5c with the alkanethiolate 2b gave 6b, whereas the reaction of 5c with the arenethiolate 2c gave a mixture of substitution product 6c and anthracene 7. The observation of the formation of both 6c and 7 is explained by the competition between substitution (SnAr) and electron‐transfer (ET) mechanisms. Consistent with this interpretation, the reaction of the monochloro‐substituted 5b, which has a higher‐energy σ* orbital, with 2c gave 6c without the formation of 7. Zn/KOH in tetraglyme was shown to reduce the aryl halides 5b–c and thio‐ether 6c to 7.