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The influence of lithium complexing agents on the regioselectivity of reductions of substituted 2-cyclohexenones by LiAlH4 and LiBH4

1980; Elsevier BV; Volume: 36; Issue: 13 Linguagem: Inglês

10.1016/0040-4020(80)80205-5

1464-5416

A. Loupy, J. SEYDEN‐PENNE,

Ammonia Synthesis and Nitrogen Reduction

A reversal of regioselectivity of LiAlH4 or LiBH4 reduction of 2-cyclohexenone induced by addition of [2.1.1]-cryptand to the reaction medium is accompanied by a rate decrease. In the absence of the cryptand, carbonyl attack predominates (C1:C3 = 86:14 with LiAlH4 in THF). In the presence of the cryptand, double bond attack is favoured (C1:C3= 14:86). This effect is larger with LiAlH4 than with LiBH4. This trend is general in the case of five substituted 2-cyclohexenones. Using 12-crown-4 as a Li+ coordinator, a change in regioselectivity occurs but it is less pronounced than with the cryptand.