Microbial hydroxylation of 2-cycloalkylbenoxazoles. Part II. Determination of product structures and enhancement of enantiomeric excess
摘要:
The determinations of product structures obtained in the microbial hydroxylations of various 2-cycloalkyl-1, 3-benzoxazoles using Cunninghamella blakesleeana DSM 1906 and Bacillus megaterium DSM 32 are described. The initially low e.e. of 3-(benz-1, 3-oxazol-2-yl)cyclopentan-1-ol 6, 2-(benz-1, 3-oxazol-2-yl)cyclohexan-1-ol 14 and 4-(2-bent-1, 3-oxazol-2-yl)cycloheptan-1-ol 21 can be enhanced to 98% using lipase catalyzed resolution.
general alkylation of heterocycles using a simple palladium catalyst is reported. Most classes of heterocycles, including indoles and pyridines, efficiently coupled with unactivated secondary and tertiary alkylhalides. An alkyl radical addition to neutral heteroarenes is most likely involved.
A matter of catalyst: Azole compounds can be directly alkylated with N‐tosylhydrazones that bear unactivatedalkylgroups (see scheme; phen=1,10‐phenanthroline, Ts=p‐toluenesulfonyl). Nickel catalysis enables the introduction of simple secondary alkyl chains into benzoxazole compounds, whereas the alkylation of 5‐aryloxazoles and benzothiazole is possible by using a cobalt catalyst.
Copper-Catalyzed Alkylation of Benzoxazoles with Secondary Alkyl Halides
作者:Peng Ren、Isuf Salihu、Rosario Scopelliti、Xile Hu
DOI:10.1021/ol300348w
日期:2012.4.6
Copper-catalyzed direct alkylation of benzoxazoles using nonactivated secondary alkylhalides has been developed. The best catalyst is a new copper(I) complex (1), and the reactions are promoted by bis[2-(N,N-dimethylamino)ethyl] ether.
Microbial hydroxylation of 2-cycloalkylbenzoxazoles. Part I. Product spectrum obtained from Cunninghamella blakesleeana DSM 1906 and Bacillus megaterium DSM 32
2-Cycloalkyl-1, 3-benzoxazoles and -thiazoles (ring sizes C-3 to C-8) were biotransformed using the title microorganisms. Products of preparative importance were (1S, 3S)-3-(benz-1, 3-oxazol-2-yl)cyclopentan-1-ol 6, (1R)-3-(benz-1, 3-oxazol-2-yl)cyclopentan-1-one 8, (1R, 2R)-2-(benz-1, 3-oxazol-2-yl)cyclohexan-1-ol 14 and the corresponding cycloheptanol and cycloheptanone derivatives.