Catalytic intramolecular hydroamination of aminoallenes using titanium complexes of chiral, tridentate, dianionic imine-diol ligands

Abstract

Earth abundant and non-toxic titanium catalysts supported by readily prepared chiral ligands catalyze hydroamination of aminoallenes that lack-protecting groups.

Jumping in the Chiral Pool: Asymmetric Hydroaminations with Early Metals

“…Aminoalcoholates of titanium ( 21a – c , 22a – c , 23a – i , 25a – i , 27a – j and 29a – h ), zirconium ( 32a – g , 33a – e ) and tantalum ( 24a – l , 26a – l and 28a – j ) ( Table 5 , Table 6 , Table 7 , Table 8 , Table 9 , Table 10 , Table 11 and Table 12 ), as well as the cyclopentadienylbis(oxazolinyl)borate group IV metal complexes 30a – c and 31 are admirable enantioselective hydroamination/cyclization catalysts for a variety of different aminoalkenes, aminodialkenes and aminoallenes, as shown by Johnson [ 90 , 91 , 92 , 93 , 94 , 95 ] and Sadow [ 56 , 58 , 96 ]. Complexes 21 – 33 commonly feature natural chiral-pool-derived ligands based on either L-valine ( 21a – c , 23a – i , 24a – l , 29e , 30a – c , 32a – g ), L-phenylalanine ( 22a – c , 25a – i , 26a – l , 27a – j 28a – j , 29a – d ), L-tert-leucine ( 31 ), L-proline ( 33a – d ) and L-pipecolic acid ( 33e ) ( Table 5 , Table 6 , Table 7 , Table 8 , Table 9 , Table 10 , Table 11 and Table 12 ).…”

“…A further modification of the earlier discussed titanium catalysts 21a – c and 22a – c ( Table 5 and Table 6 , entries 1–6), which are suitable for aminoallene ring-closing reactions, was carried out by the introduction of chiral, tridentate, dianionic imine-diol ligands at the titanium metal center, resulting in the formation of 29a – h ( 29a – e , Table 8 ; 29a – h , Table 9 ) [ 94 , 97 ]. Nevertheless, cyclization of hepta-4,5-dienylamine ( 34a ) resulted in a mixture of tetrahydropyridine 35 (40–72% yield) and pyrrolidines Z - 36 (8–17% yield) and E - 36 (17–39% yield) ( Table 8 ).…”

Recent developments in enantioselective titanium-catalyzed transformations

“…These products obtained in good to quantitative yields (51-99%) and moderate enantioselectivities (30-71% ee). catalyst 110 [112].…”

Al and Zn phenoxy-amidine complexes for lactide ROP catalysis

“…Phenoxy-imines (often abbreviated as FI) are among the most versatile ligands in coordination chemistry, 1 and their complexes have found applications in many fields ranging from catalysis 2 to pharmacology, 3 molecular magnets, 4 and sensors. 5 Their ease of access and modularity allow fine-tuning of the properties of the corresponding complexes according to the targeted application and thus access to very efficient systems.…”