Synthesis of optically active (+)-2-benzyl-, (+)-2-octyl-, and (+)-2-tetradec-5′-enylcyclobutanones via metallated chiral imines or hydrazones

Article abstract of DOI:10.1016/j.tetasy.2005.04.012

A practical asymmetric synthesis of (R)-2-benzyl-, (S)-2-octyl-, and (S)-2-tetradec-5′-enylcyclobutanones was investigated using enantiopure (S)-α-methylbenzylamine, (R)-methoxymethylbenzylamine, or hydrazine (RAMP). These amines were treated with cyclobutanone to afford the corresponding imines or hydrazones, respectively. Metallation of these imine derivatives followed by alkylation with n-octylbromide, benzylbromide, or tetradec-5-enylbromide gave, after hydrolysis, (S)-2-octylcyclobutanone and for the first time optically active (R)-2-benzylcyclobutanone and (S)-2-tetradec-5′-enylcyclobutanone (TECB) with 67-87% ee. The absolute configuration was also established.