Alkylation-Terminated Catellani Reactions by Cyclobutanol C–C Cleavage

Homoallyl alcohol as an allylation reagent for termination of the Catellani–Lautens reaction via retro-allylation

“…Further inspection of the reaction conditions revealed that the choice of NBE had a significant effect on the yield. Methyl ester of 5-norbornene-2-carboxylic acid N 2 and 5-norbornene-2-carbonitrile N 3 afforded yields similar to that with N 1 , whereas no product 4-1 was obtained with readily available norbornene derivatives N 4 , N 5 and N 6 serving as the mediator (Table 1, entries [15][16][17][18][19]. Increasing the amount of a Reaction conditions: 1a (0.3 mmol, 1.0 equiv.…”

“…To further study the generality of this reaction, the scope of amine coupling partners was investigated (Table 3). A series of functional groups on the piperidine moiety including phenyl (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), ester (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), methoxyl (4-21) ketal (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) and methyl (4-23) groups were each well tolerated. 2,6-Dimethylmo...…”

“…3 The Pd/NBE chemistry allows simultaneous functionalization of the ipso and ortho positions of simple aryl halides with different electrophiles and termination agents. A broad range of termination reactions, including Heck coupling, 4 Suzuki coupling, 5 alkyne annulation, 6 C–N coupling, 7 alkynylation, 8 hydrogenation, 9 C–H activation, 10 cyanation, 11 enolate coupling, 12 C–O coupling, 13 carbene coupling, 14 borylation, 15 thiolation, 16 selenation 17 and alkylation, 18 have been developed—and several structurally diverse poly-functionalized arenes were synthesized (Scheme 1b). Despite the broad scope of termination agents in these reactions, it is also highly desired to introduce new functional groups on the ipso positions of aryl halides to further meet the diverse goals of synthetic organic chemistry.…”

Ring-Opening Selenation of Cyclopropanol for the Selective Synthesis of β-Hydroxy-Substituted Selenylated Ketones

“…Cycloalkanol with rich reactivity has been widely employed as a readily available starting material for preparing various functionalized ketones. − In particular, cyclopropanol with larger ring tension has been proven to be a privileged precursor to synthesize diverse β-functionalized ketones via breaking the cyclic C–C bond and realizing the construction of remote C–halide (F, Cl, Br, and I), ,− C–C, − C–N, − and C–O/S − bonds. The successful synthesis of these β-functionalized ketones fully demonstrates the generality of this approach.…”

Lewis-Acid-Catalyzed Tandem Cyclization by Ring Expansion of Tertiary Cycloalkanols with Propargyl Alcohols

“…However, the cleavage of C–C σ bonds is still a great challenge for organic chemists due to the inertness and stability . Thus the C–C bond activation reactions are generally limited to highly strained small-ring compounds such as cyclopropanol and cyclobutanol, and the ring opening of cyclopentanol is quite rare . To the best of our knowledge, the ring-opening reactivity of tertiary cycloalkanols is typically upon transition-metal-catalyzed β-carbon elimination or radical-mediated ring opening (Scheme a). , For example, the Uemura, Murakami, and Cramer groups reported the ring-opening reactions of cyclobutanols via a β-carbon elimination process catalyzed by Pd, Rh, or Ru.…”