Stereocontrol of stereogenic centres para on a benzene ring using the SE2? reaction of a pentadienylsilane
作者:Ian Fleming、Colin P. Leslie
DOI:10.1039/p19960001197
日期:——
The pentadienylsilane 9 and the dimethyl acetal 2 of isobutyraldehyde react with high (80:20)anti stereospecificity to give largely the diene 10a, which was converted into the para-disubstituted benzene 11a, having 1,6-related stereogenic centres.
Alpha-Halogenoalkyl carboxylates (FG-R1CH(X)(OCOR2); FG = COOR, CN, SR; X = I, Br) were readily prepared by the addition of an acid chloride or bromide (R2COX; X = Br or Cl) to an aldehyde (FG-RCHO) in the presence of a catalytic amount of ZnCl2. They insert efficiently zinc dust in THF-DMSO (X = Br, 8-10-degrees-C, 6-10 h) affording the corresponding zinc organometallics at the a position to oxygen FG-RCH(ZnBr)(OAc). After the addition of the THF-soluble copper salt CuCN.2LiCl, the corresponding copper reagents FG-RCH(Cu(CN)ZnBr)(OAc) are formed and reacted with various classes of electrophiles such as acid chlorides, aldehydes, enones, allylic and alkynyl halides, activated alkynes, nitro olefins and alkylidenemalonates providing polyfunctional molecules in excellent yields. Similarly, zinc organometallics at the a position to the nitrogen of cyclic imides were prepared by the zinc insertion to cyclic alpha-chloromethyl (or alpha-chloroethyl) imides. After their transmetalation to the corresponding copper organometallic ((R1CO)2NCH(R)(Cu(CN)ZnCl); R = Me or H), they were reacted with allylic and alkynyl halides and ethyl propiolate affording polyfunctional imides. The reaction of cyclic N-(chloromethyl)imides with aldehydes in the presence of chromium(II) chloride in THF furnishes protected amino alcohols in 36-95% yield.
Soluble precursors convertible to tetrabenzoporphyrins below room temperature
作者:Hidemitsu Uno、Takayuki Ishikawa、Toru Hoshi、Noboru Ono
DOI:10.1016/s0040-4039(03)01265-6
日期:2003.7
Porphyrins fused with dihydroxylated bicyclo[2.2.2]octadiene at beta-positions were quantitatively converted to the corresponding tetrabenzoporphyrins either by treatment with NaH in DMF at 0degreesC or on boehmite at room temperature. (C) 2003 Published by Elsevier Science Ltd.
Aleksiev,D.I., Journal of Organic Chemistry USSR (English Translation), 1976, vol. 12, p. 1984 - 1985
作者:Aleksiev,D.I.
DOI:——
日期:——
Pillared Buserite as a new catalytic material for the 1,3-dipolar cycloaddition of α-phenyl-N-(p-methyphenyl) nitrone with electron deficient olefins
Buserite (KPB), has been used as an effective catalytic material gffor the 1,3-dipolar cycloaddition reaction of α-N-diaryl nitrone such as αphenyl-N-(p-methylphenyl) nitrone with some electron deficient olefins resulting in the exclusive formation of trans-4-substituted isoxazolidines.