title: Regioselective preparation of saturated spirocyclic and ring-expanded fused pyrazoles.
abstract: Saturated bicyclic pyrazoles represent an important class of biologically active molecules, but their preparation can be hampered by labor-intensive synthesis of required starting materials. A convenient one- or two-step procedure for the synthesis of saturated spirocyclic and fused pyrazoles is reported. The synthesis benefits from the use of readily available alkynes and bench-stable tosylhydrazones, which are easily prepared from their parent ketones. Sigmatropic rearrangement of spirocyclic pyrazoles to fused analogues occurs with concomitant one-carbon expansion of the saturated ring, allowing rapid access to a range of pharmaceutically and agrochemically relevant polycyclic structures featuring a broad scope of saturated ring sizes.
authors.affiliation: Department of Chemistry, University of Cambridge , Cambridge, CB2 1EW, U.K.
authors.forename: Rohan R
authors.initials: RR
authors.lastname: Merchant
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Allwood
authors.forename: David C
authors.initials: DC
authors.lastname: Blakemore
authors.forename: Steven V
authors.initials: SV
authors.lastname: Ley
mesh_terms: D000480:Alkynes / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry*; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000480:Alkynes; D011083:Polycyclic Compounds; D011720:Pyrazoles; D013141:Spiro Compounds