Asymmetric synthesis of cyclopropanes and dihydrofurans based on phosphine oxide chemistry

Asymmetric synthesis of trans-disubstituted cyclopropanes using phosphine oxides and phosphine boranes

“…We have achieved the synthesis of di-and trisubstituted cyclopropanes in this manner by including substituents at the a-and g-positions 5, 10 and also at the band g-positions 11, 12 of the cyclisation substrates. Recently, we reported the asymmetric synthesis of disubstituted trans-cyclopropyl ketones 3, 13 and protected trans-cyclopropane amino acids 14 using g-substituted cyclopropane precursors (Scheme 1, eq. 1).…”

Asymmetric synthesis of orthogonally protected trans-cyclopropane γ-amino acids via intramolecular ring closure

“…This was unexpected given the cyclopropanation of the related ketones (Scheme 7). 42 Treatment with potassium tert-butoxide produced cyclopropane 30 along with the two geometrical isomers of elimination product 31 (Scheme 9, Table 2). When treated with LDA, mesylate 28 produced the desired cyclopropane 30 as well as side-products 31 and 32.…”

Diphenylphosphinoyl chloride as a chlorinating agent ? the selective double activation of 1,2-diols

“…Displacement of the benzylic chlorides 5, 7 and 8 with azide produced mono-azide phosphinates 21-23 as single diastereoisomers; the phosphinate neither acts as a leaving group nor participates in the displacement of chloride. As with the related anti-azido-phosphinate, 18 syn-azido-phosphinate 21 could be converted into mainly trans-cyclopropane 31. anti-Chlorophosphinates can also be converted into anti-epoxides 27 and 29: treatment with potassium carbonate in methanol 13 results in removal of the diphenylphosphinate group 23 and ring closure. The synthesis of cyclopropane 24 30 results from the in situ basemediated reaction of epoxide 29.…”