Diastereoselective Synthesis of Medium-Sized Lactones by Cu(bpy)CI Catalyzed Cyclization of Trichloroacetates

Towards the development of highly active copper catalysts for atom transfer radical addition (ATRA) and polymerization (ATRP)‡

“…For a given transition metal, this is typically achieved using a complexing ligand. In case of copper, neutral nitrogen based ligands are typically used, ranging from bidentate (2,2 -bipyridine (bpy) (Pirrung et al, 1993(Pirrung et al, , 1994(Pirrung et al, , 1995 and N-alkyl-2-pyridylmethanimine (NAlkPMI) (Clark, 2002;Clark et al, 2000Clark et al, , 2001aClark et al, , 2001bHaddleton et al, 1997aHaddleton et al, , 1997bHaddleton et al, , 1998Lad et al, 2003), tridentate (N,N,N ,N ,N -pentamethyldiethyelenetriamine (PMDETA) (Benedetti et al, 1997;Ghelfi et al, 1999;Ghelfi & Parsons, 2000) and trispyrazolyl borate (Tp x ) (Muñoz- Molina et al, 2007Molina et al, , 2008, tetradentate (1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) , tris[2-(dimethylaminoethyl]amine (Me 6 TREN) (Clark et al, 1999(Clark et al, , 2000(Clark et al, , 2001bEckenhoff & Pintauer, 2011) and TPMA (De Campo et al, 1999, 2000Eckenhoff et al, 2012;Eckenhoff & Pintauer, 2007, 2010a, 2010b to multidentate (N,N,N ,N -tetrakis(pyridin-2-ylmethyl)ethylenediamine (TPEDA) (De Campo et al, 1999, 2000Kaur et al, 2015a). Representative examples of molecular structures of copper(I) (activators) and copper(II) (deactivators) complexes commonly used in ATRA and ATRP are shown in Fig.…”

Some Synthetic Uses of Double‐Bonded Functional Groups

“…Medium-sized lactones have also been very successfully prepared, with unexpected diastereoselectivity, by the copper(I)-catalyzed cyclization of ω-alkenyl trichloroacetates. For example, the reaction shown in equation 196 proceeded in 74% yield, producing only a single diastereomer 704 . The catalyst, Cu(bpy)Cl, has been used with other substrates to induce radical cyclizations which produce 8-and 9-membered lactones 705 (196) ω-Alkenoic acids have also been used to form 7-to 11-membered lactones, in useful yields, in a reaction that is induced by iodine(I) compounds at room temperature (equation 197) 707,708 .…”

New and improved catalysts for transition metal catalysed radical reactions

“…Thus, a new class of catalysts, most commonly transition metal complexes such as RuCl 2 (PPh 3 ) 2 , 3 FeCl 2 (P(OEt) 3 ) 3 , 4 Co(Di-Meglyoxime) 2 , 5 CuCl(bpy) 3 or a mixture of iron metal and copper bromide, 6 can be used in ATRA reactions. However, only limited success has been reported and only a few examples have appeared which describe cyclisations of allylic trichloroacetates 7 or trichloroacetamides 8 to produce g-lactones and lactams, respectively, or additions of trihalo compounds such as CCl 4 , 9 trichloroacetic acid or esters 10 to olefins. Competing telomerisation is often considered to be a drawback.…”

“…We have also observed reactions which were impossible to perform with CuCl-bpy; 7 for instance the cyclisation of hept-6-enyl trichloroacetate 3a afforded the cyclic endo lactone 3b in 70% yield in the presence of CuCl-L3 (Scheme 3). It was also possible to catalyse the exo cyclisation of prop-2-enyl trichloroacetate 4a with 48% yield in the presence of the same catalyst.…”

“…The metal could also act as a template and allow the notoriously difficult cyclisation of eight-and nine-membered ring lactone precursors as suggested previously. 7 We are currently trying to relate the redox potentials of these complexes to their catalytic activity.…”