Abstract:First, an efficient method for the synthesis of optically enriched N-fused bicyclic structures is reported. Through Mo-catalyzed desymmetrization of readily available achiral polyene substrates, 5,6-, 5,7-, and 5,8-bicyclic amides can be synthesized in up to >98% ee. The effects of catalyst structure, olefin substitution, positioning of Lewis basic functional groups and ring size are examined and discussed in detail. In the second phase of investigations, a catalytic asymmetric method for highly enantioselecti… Show more
“…In 2005, the first examples of enantioselective olefin metathesis involving substrates that bear Lewis basic amines were reported [3]. Catalytic activity of number of chiral Mo-based diolates (such as 2, Scheme 12.1) were probed; enantioselective ring-closing metathesis (RCM) reactions deliver various azacyclic structures in up to 99/1 enantiomeric ratio (er).…”
Section: Total Synthesis Of Coniine Through Enantioselective Rcm Withmentioning
“…In 2005, the first examples of enantioselective olefin metathesis involving substrates that bear Lewis basic amines were reported [3]. Catalytic activity of number of chiral Mo-based diolates (such as 2, Scheme 12.1) were probed; enantioselective ring-closing metathesis (RCM) reactions deliver various azacyclic structures in up to 99/1 enantiomeric ratio (er).…”
Section: Total Synthesis Of Coniine Through Enantioselective Rcm Withmentioning
“…[76] Enantioenriched piperidine derivatives were synthesized from trienes 119 and 122 by treatment with chiral molybdenum catalysts 121 in benzene. [77] Under these conditions, tertiary amines and neopentylic unprotected secondary amines readily underwent asymmetric RCM in good yields and enantioselectivities (Scheme 44).…”
Section: Ruthenium-catalyzed Metathesis Of Phenylamines and Analoguesmentioning
confidence: 99%
“…[85,86] This feature has also been exploited to perform RCM reaction of catechol-protected secondary amines. [77] Alternative approaches to classical RCM reaction have been reported by the group of Takeda; [87] various saturated nitrogen heterocycles such as 139 have been obtained in modest to good yields by titanocene(II)-promoted cyclization of thioacetals 138 (Scheme 52).…”
Section: Ruthenium-catalyzed Metathesis Of Phenylamines and Analoguesmentioning
Olefin metathesis is one of the most powerful synthetic tool to access amine-containing heterocycles and alkaloids. A major drawback associated with the use of amines concerns their ability to coordinate to metal-alkylidene complexes and to interfere unproductively with catalytic activity. Based on literature precedents, it has been established as a "dogma" that efficient metathesis reactions are suppressed in the presence of basic amines and that such substrates must invariably be deactivated by conversion of the amines to the corresponding carbamates or ammonium salts. However, an increasing number of examples of amine-containing compounds that are good substrates for metathesis is being reported in the literature. How can this "non-classical" reactivity be rationalized and exploited? The purpose of this review is to provide an overview of successful metathesis reactions performed with aminecontaining compounds in order to allow some guidelines to be formulated. A special emphasis is placed on the different parameters that may influence the outcome of the reaction such as steric effects, amine basicity, and the nature of the catalyst.
“…As this additional concept of enhanced sterics around the nitrogen is structurally limited and the enantioinduction moderate (71% ee), the use of different N-protecting groups was focused. 38 In this regard the Cbz-group in 66, which usually can be removed with ease, proved to be suitable. 4 efficiently promoted the ARCM in 98% yield and 95% ee with a catalyst loading of 5 mol%.…”
Section: This Journal Is C the Royal Society Of Chemistry 2012mentioning
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