Diastereoselective cyclopropanation of cyclic enones with methyl dichloroacetate anion

Ring-expansion approaches for the total synthesis of salimabromide

“…We commenced our synthesis with commercially available 5-bromo-1-indanone ( 17 ) (Scheme 3). From there, cyclopropanated indanone 21 was generated in six steps involving a three-step methylation procedure ( 17 to 18 to 19 ) [16,17], a bromination with copper(II) bromide ( 19 to 20 ) [18,19] followed by elimination and subsequent cyclopropanation with methyl dichloroacetate (MDA, 20 to 21 ) [13,20]. The fragmentation was conducted in sulfolane at 190 °C affording naphthol 22 in good yield (77%) on gram-scale [13].…”

Ring Opening of Bicyclo[3.1.0]hexan‐2‐ones: A Versatile Synthetic Platform for the Construction of Substituted Benzoates

“…= 4:1), which are readily available from the reaction of 3-methyl-2-cyclopenten-1-one with the lithium enolate of inexpensive methyl dichloroacetate (Scheme 1). [9] Conceptually,w ee nvisioned the mixture of the cis-trans and cis-cis diastereomers 1a and 1b,r espectively,t ou ndergo athermally allowed cyclopropyl allyl cation type ring opening (2p disrotatory) to afford 2. [10] Fort he initial ring-opening step,t he CÀCb ond cleavage with concomitant loss of chloride,w ee xpected the reaction rate of 1a and 1b to be governed by the relative orientation of the substituents to the leaving group.…”

“…Based on these preliminary results,w ei nvestigated the conversion of diastereomerically pure 5 [9] into 6 under varying reaction conditions (Table 1). An examination of various solvents established that the reaction is efficiently promoted by polar, high-boiling solvents and proceeds fastest in sulfolane at 190 8 8C( entries 1-4).…”

Ring Opening of Bicyclo[3.1.0]hexan‐2‐ones: A Versatile Synthetic Platform for the Construction of Substituted Benzoates

“…[2] Conventional syntheses of polysubstituted 3-hydroxybenzoates from either aromatic (linear assembly) or acyclic (convergent assembly) precursors are complicated by difficulties arising from low reactivity and poor selectivity (Figure 2a,m ethods A-C). [9] Conceptually,w ee nvisioned the mixture of the cis-trans and cis-cis diastereomers 1a and 1b,r espectively,t ou ndergo athermally allowed cyclopropyl allyl cation type ring opening (2p disrotatory) to afford 2. [3] Form ethod B, the directing electronic effects of the ester and electron-donating substituents (Y = OR, NRR') are mismatched and result in poor regioselectivity.Strategies based on the [4+ +2] cycloaddition of dienes with alkynoates (method C) usually require symmetrical substrates to allow formation of the desired 1,3-orientation.…”