Improved methods for the reductive alkylation of methoxybenzoic acids and esters: applications to the synthesis of bicyclic ketones

Homolytic dissociation of 1-substituted cyclohexa-2,5-diene-1-carboxylic acids: an EPR spectroscopic study of chain propagation†

“…Birch reduction-alkylation of benzoic acid affords 1-alkylcyclohexa-2,5-dienecarboxylic acids of type 1 in moderate to good yields. [4][5][6][7][8][9] The 1-alkyl acids 1a-l were obtained in various yields by means of a modification of the procedure due originally to Birch. 4 The method was most efficient for primary and secondary alkyl substituents and particularly with benzyl chloride, allyl and propargyl bromides.…”

Asymmetric Conjugate Addition to α-Substituted Enones/Enolate Trapping

“…We then focused on a key intermediate of the synthesis of guanacastepene A. , Since the direct trapping using methyl vinyl ketone (MVK) led to a complex mixture, we opted for a synthetic equivalent. Addition of trimethylsilyl iodide to MVK generated (4-iodobutenyloxy)trimethylsilane 28 in situ, which was reacted with the magnesium enolate . The iodine of 28 is then displaced to afford 3-isopropyl-2-methyl-2-(3-oxobutyl)cyclopentanone ent-29 in 92:8 er and 68:32 dr after acidic workup (Scheme C).…”

Formation of Contiguous Quaternary and Tertiary Stereocenters by Sequential Asymmetric Conjugate Addition of Grignard Reagents to 2‐Substituted Enones and Mg–Enolate Trapping

“…This is due to the competitive pathways between enolates that lead to an alternative pathway, oligomerization. The problem could be circumvented by choosing allyliodide derivative 45 , which was formed after the reaction of MVK with trimethylsilyliodine in dichloromethane at low temperature 20. The resulting 1,5‐diketone could be isolated in 45 % yield after reaction of 44 and the Mg–enolate, which were both formed in situ (Scheme ).…”

“…The problem could be circumvented by choosing allyliodide derivative 45,w hich was formed after the reactiono fM VK with trimethylsilyliodine in dichloromethane at low temperature. [20] The resulting 1,5-diketonec ould be isolated in 45 %y ield after reaction of 44 and the Mg-enolate, which were both formed in situ (Scheme 7). The synthesis of 42 and analogues addresses the need for enantioenriched trisubstituted cyclopentanones in natural products syntheses, notably in bioactive terpenoids.…”