Direct observation of reaction intermediates for a well defined heterogeneous alkene metathesis catalyst
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It is shown how selective high resoln. 2-dimensional NMR spectra can be obtained which feature multiplets where all peaks have the same pos. sign and pure absorption lineshapes. [on SciFinder (R)] ...
New 2-dimensional NMR correlation methods are presented which allow one to obtain selected high-resoln. multiplets where all signals have pos. pure absorption peak shapes. The multiplets do not suffer from any cancellation effects, and their fine structure ...
Me groups adjacent to an olefinic double bond were metalated by KOCMe3 and BuLi without cis-trans isomerization. Thus, (E)-MeCH:-CHMe was metalated to give (E)-MeCH:CHCH2K (I) which reacted with ethylene oxide to give 41% (E)-MeCH:CH(CH2)3OH. If I was allo ...
Unstabilized P ylides and their betaines added Li salts, losing most of their reactivity, and were reactivated with tert-BuOK, making thus possible the retardation or the acceleration of the Wittig reaction. The C:O olefination often yielded an isomer mixt ...
New NMR techniques are described for transferring transverse magnetization between scalar-coupled nuclei in the rotating frame. The methods involve simultaneous spin-locking of two selected spins A and X, using cosinusoidal modulation of the radio frequenc ...
A technique is proposed which simplifies the study of spin-lattice relaxation in multilevel nuclear spin systems. The introduction of non-participating "spy" nuclei, which interact with the nuclei under investigation through scalar or dipolar coupling, m ...
A review, with 6 refs., of the prepn. of olefins from phosphonium ylides and carbonyl compds. and from phosphonium ylides, carbonyl compds., org. Li compds., and reactive halogen compds., such as MeCOCH2Cl and EtI. [on SciFinder (R)] ...
Olefins of the formula R1XC:CR2R3 were prepd. by removal of a proton from a betaine-like intermediate, (Ph)3P+-CHR1CR2R3O-, and subsequent treatment with the desired X+. Thus, 1 mole PhLi and the phosphonium salt, (Ph)3PCH2R1.HCl, in 3 parts Et2O and 1 par ...
Phosphorylide complexes, Li+[Ph3P+C-HR]X-, where R = H, alkyl, or alkoxy, gives very poor yields of olefins from aldehydes in the Wittig reaction. In the presence of 1.1 equivs. tert-BuOK the reaction is strongly accelerated. By this method methylenecycloh ...
