New synthetic reactions. Synthesis of cyclobutanes, cyclobutenes, and cyclobutanones. Applications in geminal alkylation

Ruthenium catalyzed dimerization–ring expansion reaction of acetylenylcyclobutanols

“…% CpRu(MeCN) 3 PF 6 7 in DMF at 60°C (Table 1). Although no reactions proceed from the substituted alkynes 3a-3d (entries 1-4), the ring expanded product 5 accompanied by a dimerization process is obtained from the reaction of 3e, in 41% yield (entry 5).…”

Tetrafluoroboric Acid

“…Some adducts obtained upon reaction of cyclopropyl phenyl sulfide anion with carbonyl compounds can be rearranged to cyclobutanones under the catalytic influence of HBF 4 (eq 4), although different acids have been required for other substrates. 10 Acidcatalyzed rearrangement of 2-cyclopropylphenyl phenyl ether or sulfide with HBF 4 has been reported (eq 5). 11 Other catalytic applications of HBF 4 include alkene isomerizations, 14 alkylation of alcohols with diazoalkanes, 15 preparations of substituted pyridines, 16 hydrolysis of α-hydroxyketene or α-(methylthio)ketene thioacetals to α,β-unsaturated thioesters, 17 and terpene formation from isoprenic precursors.…”

Phenylthiocyclopropanea,c

“…The more general and vigorous conditions involve the use of Tin(IV) Chloride in methylene chloride (eq 14). 32 Protic acids with a nonnucleophilic anion, such as 48% aqueous Tetrafluoroboric Acid, work nicely with β-hydroxy sulfides derived from sterically unhindered ketones, but increasing steric hindrance led to no reaction. 32 The reaction has also been performed with p-Toluenesulfonic Acid in wet benzene 32 or tetralin.…”

“…32 Protic acids with a nonnucleophilic anion, such as 48% aqueous Tetrafluoroboric Acid, work nicely with β-hydroxy sulfides derived from sterically unhindered ketones, but increasing steric hindrance led to no reaction. 32 The reaction has also been performed with p-Toluenesulfonic Acid in wet benzene 32 or tetralin. 26 These conditions require heating and are particularly useful for the adducts derived from saturated aldehydes.…”

“…26 These conditions require heating and are particularly useful for the adducts derived from saturated aldehydes. 32 They have been used for the synthesis of the parent cyclobutanone 26 (70-120 • C in the presence of Mercury(II) Chloride as a thiol trap). The rearrangement is stereoselective.…”