Abstract
AbstractDiastereomerically pure 3‐[(trimethylsilyl)oxy]oxetanes 3 were prepared in moderate to good yields (45–72%) by the Paternò‐Büchi reaction of silyl enol ethers 2 with benzaldehyde. The photocycloaddition exhibits a high degree of regio‐ and diastereoselectivity. The substituents R in the silyl enol ether have been varied [R = Me, Et, iPr, tBu, Ph, CH(OMe)2, CH(OCH2)2, C(OCH2)2Me], and it was found that steric bulk is mainly responsible for enhanced selectivity (diastereoselectivity from 70:30 up to 95:5). The regiochemical control is perfect (regioselectivity >95:5) except for silyl enol ether 2a (R = Me) in the case of which a 90:10 ratio of regioisomers was observed. Irradiation of the reaction mixture at lower temperature (–25°C) led to a further improvement of diastereoselectivity. The relative configuration of the products obtained was elucidated both by 1H‐NMR spectroscopy and by chemical degradation. As a mechanistic hypothesis to explain the high observed diastereoselectivity we propose that the steric environment in the intermediate diradical 11 determines the selectivity according to two possible reaction pathways, i.e. bond formation and retrocleavage.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
