A concise and enantioselective approach to cyclobutanones by tandem asymmetric epoxidation and enantiospecific ring expansion of cyclopropylidene alcohols. An enantiocontrolled synthesis of (+)- and (-)-.alpha.-cuparenones
摘要:
A tandem Katsuki-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alkyl(or 1-aryl)-1-(hydroxymethyl)cyclobutanones (3a-i) in high yields and high enantiomeric excess. These compounds are potentially valuable synthons for the enantioselective creation of the quaternary carbons. Hence, this enabled us to accomplish a concise and enantioselective total synthesis of both (+)- and (-)-alpha-cuparenones (11).
Enantioselective Synthesis of γ-Aryl-γ-butyrolactones by Sequential Asymmetric Epoxidation, Ring Expansion, and Baeyer−Villiger Oxidation
作者:Bin Wang、Yu-Mei Shen、Yian Shi
DOI:10.1021/jo061341j
日期:2006.12.1
N-tolyl-substituted oxazolidinone-containing ketone as catalyst and Oxone as oxidant via a sequential asymmetric epoxidation of benzylidenecyclopropanes, ring expansion, and Baeyer−Villigeroxidation. Up to 91% ee was obtained. Optically active cyclobutanones can also be obtained by suppressing the Baeyer−Villigeroxidation with use of more ketone catalyst and less Oxone.
The cyclopentenone 8, synthesised by palladium mediated ring expansion of the chiral vinylcyclobutanols 3 and 4, is converted to the thermodynamically unstable ketone 16 which on methylenation gives (+)-laurene 1.
作者:Melanie A. S. Blackburn、Corin C. Wagen、M. Raul Bodrogean、Pamela M. Tadross、Andrew J. Bendelsmith、Dennis A. Kutateladze、Eric N. Jacobsen
DOI:10.1021/jacs.3c02960
日期:2023.7.19
A catalytic protio-semipinacol ring-expansion reaction has been developed for the highly enantioselective conversion of tertiary vinylic cyclopropyl alcohols into cyclobutanone products bearing α-quaternary stereogenic centers. The method relies on the cocatalytic effect of a chiral dual-hydrogen-bond donor (HBD) with hydrogen chloride. Experimental evidence is provided for a stepwise mechanism where
A concise and enantioselective approach to cyclobutanones by tandem asymmetric epoxidation and enantiospecific ring expansion of cyclopropylidene alcohols. An enantiocontrolled synthesis of (+)- and (-)-.alpha.-cuparenones
A tandem Katsuki-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alkyl(or 1-aryl)-1-(hydroxymethyl)cyclobutanones (3a-i) in high yields and high enantiomeric excess. These compounds are potentially valuable synthons for the enantioselective creation of the quaternary carbons. Hence, this enabled us to accomplish a concise and enantioselective total synthesis of both (+)- and (-)-alpha-cuparenones (11).
A concise enantiocontrolled total synthesis of (−)-α-bisabolol and (+)-4-epi-α-bisabolol
chiral cyclobutanone 3 was effectively achieved with [1,4-bis(diphenylphosphino)butane](1,5-cyclooctadiene)rhodium (1) tetrafluoroborate as catalyst to give the olefins 7 and 8 which were converted into (−)-α-bisabolol 1a and (+)-4-epi-α-bisabolol 15via9 and 10, 11 and 12, and 13 and 14.