Morita−Baylis−Hillman Reaction of Masked 5-Alkylidene-2-cyclopentenones:  General Entry to 5-Alkylidene-2-(hydroxyalkyl)- 2-cyclopentenones

Abstract

The reaction of masked 5-alkylidene-2-cyclopentenones with aldehydes catalyzed by tributylphosphine in the presence of phenol provided the corresponding Morita-Baylis-Hillman adducts, which were subjected to flash vacuum pyrolysis to afford 5-alkylidene-2-(hydroxyalkyl)-2-cyclopentenones.

Recent Contributions from the Baylis−Hillman Reaction to Organic Chemistry

“…Pohmakotr and co-workers 151 employed 5-spiroalkylidenecyclopent-2-enones (13) as activated alkenes for the Baylis-Hillman coupling with aldehydes, under the influence of PPh 3 , to provide the resulting Baylis-Hillman alcohols as a mixture of stereoisomers, which on subsequent flash vacuum pyrolysis (FVP) afforded 5-alkylidene-2-(hydroxyalkyl)cyclopent-2-enones, following the reaction sequence shown in Scheme 19. One representative example is presented.…”

Retracted article: Enantioselectivity of aza-MBH-type reaction of nitroalkene to N-tosylimine catalyzed by thiourea-tertiary amine: a theoretical study

“…[8][9][10][11] Recently, Pohmakotr has described an asymmetric MBH reaction catalyzed by tributylphosphine in the presence of phenol. 12 Verkade isolated the MBH type adducts employing P(PhCH 2 NCH 2 CH 2 ) 3 N as an efficient catalyst. 13 Without Lewis acid or base, the a-acylvinyl anion equivalents could still undergo highly selective addition to imines generating b-substituted aza-MBH-type adducts.…”

Silver(I)-Catalyzed Ring-Contractive Rearrangement: A New Entry to 5-Alkylidene-2-cyclopentenones

“…Furthermore, molecules with a cyclopentenone (especially alkylidene-2-cyclopentenone) motif, such as Δ 7 -PGA 1 , punaglandin 4, and leucodin, are important in natural products and pharmaceuticals. Although there are known synthetic strategies for alkylidene-2-cyclopentenone units including Nazarov cyclization, sulfoxide elimination followed by retro-Diels–Alder reaction, condensation/dehydration elimination, and so on, , all these methods involve multistep operations and have limitations in terms of atom economy. Thus, there is an urgent demand in developing efficient, versatile, and practical protocols for the synthesis of 5-alkylidene-2-cyclopentenones.…”