Detail of "6436-90-4"

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Photoaddition reactions of acenaphthylenedione with a-silyl n-electron donors via triplet single electron transfer desilylation and triplet hydrogen atom abstraction pathways

Photoaddition reactions of acenaphthylenedione with a-silyl n-electron donors via triplet single electron transfer desilylation and triplet hydrogen atom abstraction pathways.Some chemicals with cas registry numbers like 6436-90-4 and 138858-24-9 are also used. Yoon, Ung Chan; Kim, Yong Chul; Choi, Jeong Ja; Kim, Dong Uk; Mariano, Patrick S.; Cho, In Seop; Jeon, Yoon Tag (Dep. Chem., Pusan Natl. Univ., Pusan 609-735, S. Korea). J. Org. Chem., 57(5), 1422-8 (English) 1992. CODEN: JOCEAH. ISSN: 0022-3263. DOCUMENT TYPE: Journal CA Section: 29 (Organometallic and Organometalloidal Compounds) Section cross-reference(s): 22 Single electron transfer (SET) induced photoaddn. reactions of acenaphthylenedione (ACND) with the n-electron donors Et2NCH2SiMe3, n-PrSCH2SiMe3, EtOCH2SiMe3, EtCO2CH2N(CH2Ph)CH2SiMe3, and EtCO2CH2N(CH2Ph)CH3 are explored. Photoaddn. of Et2NCH2SiMe3 to ACND occurs in MeOH and MeCN to produce 2-hydroxy-2-[(diethylamino)methyl]acenaphthylen-1-one. In contrast, photoaddn. of n-PrSCH2SiMe3 to ACND generates two photoadducts, 2-hydroxy-2-[(n-propylthio)methyl]acenaphthylen-1-one and 2-hydroxy-2-[(n-propylthio)(trimethylsilyl)methyl]acenaphthylen-1-one, along with an ACND photoredn. dimer. Photoaddn. of EtOCH2SiMe3 to ACND produces two diastereomers of 2-hydroxy-2-[ethoxy(trimethylsilyl)methyl]acenaphthylen-1-one along with the redn. dimer. The formation of all photoproducts in these reactions is quenched by oxygen, indicating that the triplet of ACND is the reactive excited state. Based on a consideration of the oxidn. potentials of the a-silyl n-electron donors, and the nature of photoproducts, mechanisms for these photoaddns. involving triplet SET-desilylation and triplet H-atom abstraction pathways are proposed. Photoaddn. of EtCO2CH2N(CH2Ph)CH2SiMe3 to ACND provides two major products, 2-hydroxy-2-[[N-benzyl-N-(carbethoxymethyl)amino]methyl]acenaphthyle n-1-one and 2-hydroxy-2-[[N-benzyl-N-[(trimethylsilyl)methyl]amino]carbethoxymethyl] acenaphthylen-1-one along with several minor products. The formation of the major products via sequential SET-deprotonation pathways shows that the electron-withdrawing carbethoxy substituent serves to control the regioselectivity for deprotonation of the amine radical cation intermediate. Photoaddn. studies of EtCO2CH2N(CH2Ph)Me also demonstrate the effect of the electron-withdrawing carbethoxy substituent on amine radical cation deprotonation regiochem. .

New strategy for the synthesis of 3-substituted prolines

New strategy for the synthesis of 3-substituted prolines. Karoyan, Philippe; Chassaing, Gerard (Lab. Chimie Organique Biologique, Univ. P. et M. Curie, Paris 75252, Fr.). Tetrahedron Letters, 38(1), 85-88 (English) 1997 Elsevier. CODEN: TELEAY. ISSN: 0040-4039. DOCUMENT TYPE: Journal CA Section: 34 (Amino Acids, Peptides, and Proteins) Ring formation involving a 5-exo trig cyclization between a zinc enolate and a nonactivated double bond led to cis diastereoisomer of 3-substituted prolines. This cyclization was achieved with transfer of chirality onto the C-2 carbon when the nitrogen was protected by an a-methylbenzyl group. Reprotonation of the lithium enolate of the cis deriv. yielded the trans diastereoisomer. Thus, deprotonation of (S)-PhCH(Me)N(CH2CH2CH:CH2)CH2CO2Et at -78° with LDA in Et2O, followed by addn. of ZnBr2 at -90°, warming to room temp., and quenching with water gave a ratio of cis ester I. Hydrogenolysis of I, followed by sapon. gave (2S,3R)-3-methylproline II. Epimerization of cis ester (±)-III with NaOEt in EtOH gave a 55/45 trans/cis isomer ratio, while deprotonation with LDA in THF and quenching with EtOH gave a 77/23 ratio of trans/cis isomers, which could be sepd. chromatog.Except for chemicals metioned above, 6436-90-4 and 186586-61-8 are also used. .