Allylic sulfamate esters

Investigations by both Katsuki and Che have highlighted the application of chiral Mn(III) salen complexes for asymmetric N-atom transfer reactions (Fig. 17) [79-81]. In the former case, the use of [Mn(salen)PF6] together with PhI= Ts affords modest product yields and enantiomeric ratios for amination of simple benzylic and allylic starting materials. A high-valent Mn imido species is presumed to be the active oxidant. Methodological and mechanistic studies conducted by Che have found that the same types of Mn(III) salen complexes will induce oxidative cyclization of sulfamate esters. Although these catalysts afford... 

A highly effective Ru-eatalyzed asymmetric intramolecular amination of benzylic and allylic C—H bonds was developed in 2008 by Blakey and coworkers. Ru-Pybox complexes were readily prepared by using Nishiyama s method. Initially, the reaction was tested without any additives. However, the desired product 133 could be produced in only modest yields and ee values (Table 1.10, entries 1-3). Based on the studies by Du Bois, the authors rationalized that a cationic catalyst would be more reactive than the neutral one. Thus, the catalyst prepared from halide abstraction by AgOTf gave improved yields and selectivities (Table 1.10, entries 4-6). Further screening of ligands, solvents, and temperature led to the optimal conditions reaction of sulfamate ester 132 with 5 mol% of C16,110 mol% of PhI(OAc)2, and 230 mol% of MgO in benzene at 4 °C (Table 1.10, entries 7-14). Under these conditions, a series of five- and six-membered-ring products were obtained with up to 71% yield and 92% ee. Notably, the cis-olefin substrate 135 could also participate in the reaction (Scheme 1.50). Under the standard conditions, the... 

It was suggested that in the photochemically triggered oxidation of phenol by Ru(bpy)3, the proton charge was delocalized over a primary shell of water molecules firmly bound to the pyridinium cation.The tetra-2-oxypyridinate ruthenium(II, III) dimer [Ru2(hp)4Cl] and related diruthenium adducts were effective catalyst for the oxidation of allylic and benzylic C—H bonds. The bis(homoallylic) sulfamate esters were converted to the corresponding allylic amines using PhI(02C Bu)2 in CH2CI2. Both computational and experimental studies favoured a stepwise mechanism involving H atom abstraction/radical recombination and the intermediacy of a discrete short-lived diradical species. ... 

Alkylideneaceto-acetic esters Allylumlagerung Allyl rearrangement Ameisensaure Formic acid Amldosulfonsaure Sulfamic acid Anhydrozucker Anhydrosugars Anlagerung Addition Arylierung Arylation Asparaginsauren Aspartic acids Aufbau Synthesis Austausdi Replacement Benzopersaure... 

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