Cross-coupling reaction of organosilicon nucleophiles
申请人:——
公开号:US20020183516A1
公开(公告)日:2002-12-05
Improved methods for generating a —C—C— bond by cross-coupling of a transferable group with an acceptor group. The transferable group is a substituent of an organosilicon nucleophile and the acceptor group is provided as an organic electrophile. The reaction is catalyzed by a Group 10 transition metal complex (e.g., Ni, Pt or Pd), particularly by a palladium complex. Certain methods of this invention use improved organosilicon nucleophiles which are readily prepared, can give high product yields and exhibit high stereo selectivity. Methods of this invention employ activating ions such as halides, hydroxide, hydride and silyloxides. In specific embodiments, organosilicon nucleophilic reagents of this invention include siloxanes, particularly cyclic siloxanes. The combination of the cross-coupling reactions of this invention with ring-closing metathesis, hydrosilylation and intramolecular hydrosilylation reactions provide useful synthetic strategies that have wide application.
NOBF4 underbasic or even almost neutral reaction conditions. Acid-sensitive functional groups are tolerated under the developed basicconditions. For the substrates having poor reactivity, almost neutralconditions (using pyridine equimolar to NOBF4) are suitable for better yields. Furoxans (1,2,5-oxadiazole 2-oxides) can be synthesized from the corresponding styrenes using NOBF4 underbasic or even
corresponding styrenes usingnitrosoniumtetrafluoroborate as the nitrosation reagent in pyridine (basic media) or dichloromethane (neutral media). Acid‐sensitive functional groups were tolerated under these conditions. The probable reaction mechanism was elucidated. The experimental results support an ionic reaction pathway in contrast to the conventional acidic conditions with a radical mechanism.