Samarium isopropoxide

Reductive acylation. Acetates are generated from carbonyl compounds in a Meerwein-Ponndorf-Verley reduction in the presence of isopropenyl acetate. Beside gadolinium(in) isopropoxide, samarium isopropoxide can also be used to induce the reaction. 

Scheme 20.7 Racemization of (S)-l-deutero-1-phenylethanol (9) with deuterated samarium(lll) isopropoxide (17).

The mechanism of the MPVO reactions has been investigated and questioned on several occasions, and a variety of direct hydrogen-transfer pathways have been suggested (see Scheme 20.4) [31-35]. Recently, racemization of D-labeled 1-phenylethanol with deuterated samarium(III) isopropoxide (17) proved that the MPVO reaction occurs via a direct hydrogen transfer from the a-position of the isopropoxide to the carbonyl carbon of the substrate (Scheme 20.7) [31]. 

Pyrroles. Imines and nitroalkenes undergo condensation to afford 1,3,4-trisubsti-tuted pyrroles. For the promotion of this reaction, samarium(ni) isopropoxide is better than several other Sm compounds and isopropoxides of lanthanum and ytterbium. 

Samarium, neodynium, and yttrium isopropoxide have been used in combination with benzyl alcohol, which is a transfer agent, for the -CL polymerization. The catalytic activity is higher compared with aluminum and zirconiiun coim-terparts. The apparent propagation rate constant first increases with the alco-hol/metal molar ratio up to an optimum value, and then decreases according to an egg-shaped curve (20,57). Once again, the use of a catal5d ic amount of lanthanide alkoxides is a valuable strategy to decrease the polyester contamination by metallic residues. 

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