Cyclobutanone und Cyclobutenone in der Natur und in der Synthese

Synthetic applications of gold-catalyzed ring expansions

“…Substituted cyclobutanones [13–15] and cyclopentanones [16–18] constitute valuable building blocks in organic synthesis due to their rich chemistry. In addition, they are common motifs in numerous natural products.…”

Concise synthesis of functionalized benzocyclobutenones

“…1 Ring-opening of benzocyclobutenones is known to be triggered by heat 2 or nucleophiles, 3 and also known to be facilitated by transition metals. 4 Combining further reactions of metal-carbon bonds, transition metal-mediated C–C bond cleavage of benzocyclobutenones can lead to new transformations for preparing novel structures.…”

Alkoxide-induced ring opening of bicyclic 2-vinylcyclobutanones: A convenient synthesis of 2-vinyl-substituted 3-cycloalkene-1-carboxylic acid esters

“…In particular, due to their facile accessibility [3–8] and expeditious ring transformations, the use of cyclobutanones as extremely versatile and useful starting materials or intermediates in the construction of carbon skeletons has flourished over the past three decades [9–10]. In addition, the high electrophilicity of the carbonyl carbon atom, and the puckering of the cyclobutane caused by the substitution at C-2 and C-4, also offer both interesting preparative and mechanistic aspects [11]. The ease of ring opening of cyclobutanones is influenced by the strain of the four-membered rings, the substitution pattern on the ring, and the properties of the reagents as well as the reaction conditions.…”

“…In particular, the ring opening of certain fused-ring cyclobutanones, which are easily prepared by the well-established [2 + 2] cycloadditions of ketenes with various cycloalkenes, has been extensively investigated [3–8 12–14]. To achieve the ring opening, many reaction conditions have been investigated, such as acidic conditions, basic conditions, nucleophilic attack, thermolysis, and oxidizing as well as reducing conditions [4,11]. Cohen and Matz described the [1,2]- and [1,3]-acyl migration of 2-vinylcyclobutanones, leading to cyclopentenones or cyclohexenones, respectively [15].…”