Ring cleavage reaction based on intermolecular aldol condensation

Abstract

Acetalization of carbonyl groups in cyclic ketones using BF3-ethylene glycol brought about ring cleavage reactions via an intermolecular aldol condensation.

Synthesis of (E)-1-Aryl-1-alkenes via a Novel BF3·OEt2-Catalyzed Aldol−Grob Reaction Sequence

“…The yields were dependent on the electronic nature of the substituent, being generally higher in instances where electronwithdrawing groups were present, a fact attributed to the stability of the styrenyl products under the reaction conditions. Chloro-, bromo-, methoxycarbonyl-, carboxyl-, and trifluoromethyl-substituted benzaldehydes gave the corresponding alkenes in good to excellent yields (Table 5,8,(10)(11)(12). However, the presence of strong electron-withdrawing groups such as nitro and cyano led to lower yields of the corresponding alkenes.…”

“…( as the acid-catalyzed fragmentation of β-hydroxyacetals. 12,13 Grob fragmentations have been reported in numerous syntheses including the preparation of mediumsized carbocycles, 14 hormones, 15 pharmaceuticals, 16 and carbohydrates. 17…”

An Unprecedented, Tandem Aldol−Grob Reaction Sequence

“…A reasonable mechanism would involve the formation of the mixed aldol followed by the formation and subsequent nonsynchronous ring opening of a lactol as shown in Scheme . The proposed fragmentation is reminiscent of two-step Grob fragmentations that have been reported for N -halo-α-amino acids and cyclobutane hemiacetals as well as the acid-catalyzed fragmentation of β-hydroxy acetals. , Grob fragmentations have been reported in numerous syntheses including the preparation of medium-sized carbocycles, hormones, pharmaceuticals, and carbohydrates 1 …”

A New Synthesis of Alkenes via a Boron Trifluoride Mediated Reaction of Aliphatic Ketones with Aromatic Ketones

“…A reasonable mechanism would involve the formation of the mixed Aldol product followed by the formation and subsequent nonsynchronous ring opening of a lactol which is reminiscent of the two step Grob 5 fragmentation that has been reported for N-halo-α-amino acids 6 and cyclobutane hemiacetals 7 as well as the acid catalysed fragmentation of β-hydroxy acetals. 8,9 In conclusion, we have developed a new reaction in which aromatic ketones are converted into alkenes via reaction with aliphatic ketones.…”