Ketones, dibenzyl crystal structure

Cyclic ketone dianions obtained by the condensation of 1,4-dilithio-1,3-dienes with carbon monoxide can be used for the one-pot synthesis of a variety of 3-cyclopentenone derivatives20. Treatment of the dilithio species with 2 equivalents of benzyl bromide gave the corresponding 2,5-dibenzyl 3-cyclopentenone in 73% yield. A single-crystal structure analysis revealed that the two benzyl groups are in a trans orientation. Several examples of the one-pot synthesis of 3-cyclopentenone derivatives using this method are summarized in Table 7. 

Monomeric lithium enolates were rarely characterized by crystal structure analysis. It seems that prerequisite to monomer formation is an optimal solvation of the counterion lithium only if the metal is satisfied by a threefold, strong coordination by an external cosolvent, a monomeric enolate was detectable in the crystal state. This is illustrated by a crystal structure of the lithium enolate of dibenzyl ketone grown from a THF/diethyl ether solution containing the tri-dentate amine ligand A/ M M M" M"-pentamethyldiethylenetriamine (PMDTA), shown in Figure 3.4 [16a]. 

An uncharacteristic enolate coordination is observed for the a,a -ketodianion derived fiom dibenzyl ketone (158).Hie dianion crystallizes as a bis-TMEDA solvate with the general structure shown as (159). Hie two lithium atoms are on opposite sides of the relatively planar carbon skeleton. Each is solvated by TMEDA. Besides coordination to the oxygen, the lithium atoms are in close contact with four additional carbon atoms. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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