Diastereoselective manipulations of bicyclo[m.1.0]alkane derivatives. 5. α′-alkylations of bicyclo[m.1.0]alkan-2-ones

Diastereoselective Manipulations of Bicyclo[m.1.0]alkane Derivatives. 6. Stereocontrolled Synthesis of Tricyclo[m.n.0.0]alkenones

“…Deprotonation of 1c with LDA and alkylation with 2-methyl-3-bromopropene produced 16 in 61% yield. Here again, diastereoselectivity was high (>20:1), and stereochemistry was assigned in accord with previous work …”

“…Here again, diastereoselectivity was high (>20:1), and stereochemistry was assigned in accord with previous work …”

“…Both alkylations gave products with >20:1 diastereoselection . Stereochemistry was assigned in accord with our previous observations and assignments 1 Sequential Alkylations of Bicyclo[ m .1.0]alkan-2-ones 1 a − c a Diastereomer ratio determined by 13 C NMR analysis.…”

“…Mixtures of diastereomers were obtained for these alkylations. This fact was previously attributed to the ease of epimerization of the stereogenic center at C-3 in this ring system …”

“…Variants of these reactions that afford absolute stereocontrol have been described . Recently, we demonstrated that sequential alkylations of enolates derived from bicyclo[ m .1.0]alkan-2-ones 1a − c with different electrophiles afforded 3,3-dialkylbicyclo[ m .1.0]alkan-2-ones in a stereocontrolled manner . Stereocontrol was attributed to steric impedance to approach of the electrophile due to the cyclopropane methylene.…”