Epoxydiazo ketones. Synthesis and reactions

Improved Arndt−Eistert Synthesis of α-Diazoketones Requiring Minimal Diazomethane in the Presence of Calcium Oxide as Acid Scavenger

“…Furthermore, a highly efficient synthetic procedure for the preparation of 1-bromo-3-diazopropan-2-one (6a, Scheme 2), as well as the analogous chloro derivative 6b via the reaction of minimal amounts of diazomethane with the corresponding acid halides, is an important goal since diazoketones 6a,b represent versatile scaffolds in organic synthesis. In fact, diazoketones 6a,b may be employed in a plethora of transformations such as heteroatom alkylation, [24][25][26][27] Darzens condensation, 28 benzene alkylation, 29 or diazo displacement reactions. 30 In this way, treatment of 5a with a freshly prepared and titrated (0.27 M) ethereal solution of diazomethane (1.0 equiv) in the presence of CaO (1.1 equiv) cleanly afforded the expected R-diazoketone 6a in quantitative isolated yield, without the formation of any side product (Scheme 2).…”

“…Furthermore, a highly efficient synthetic procedure for the preparation of 1-bromo-3-diazopropan-2-one ( 6a , Scheme ), as well as the analogous chloro derivative 6b via the reaction of minimal amounts of diazomethane with the corresponding acid halides, is an important goal since diazoketones 6a , b represent versatile scaffolds in organic synthesis. In fact, diazoketones 6a , b may be employed in a plethora of transformations such as heteroatom alkylation, − Darzens condensation, benzene alkylation, or diazo displacement reactions …”

TBAF-Triggered Aldol-Type Addition of α-Triethylsilyl-α-diazoacetone

“…The aldol-type addition of (diazomethyl)­carbonyl moieties A with various aldehydes provides a convergent route to β-hydroxy-α-diazocarbonyl intermediates B (Scheme ). This reaction is usually achieved under strongly basic conditions (KOH, NaOH, LDA, CH 3 MgBr, DBU). This methodology takes advantage of the good stability displayed by the diazo moiety of diazocarbonyl compounds in basic media.…”

“…Indeed, TES-diazoacetone underwent an unprecedented LDApromoted methyl-side aldolization. Complete removal of the TES protecting group by methanolysis provided diazoaldol C. The latter was involved in a LDA-mediated diazo-side aldoltype addition, leading to diversely substituted 2-diazo-3-oxo-1,5-diols D. Clean 1,2-H migration induced by Rh 2 (OAc) 4 provided the corresponding 5-hydroxy-1,3-diketones E, mainly as their keto−enol tautomeric form. These results prompted us to investigate further the synthetic interest of the triethylsilyl moiety of TES-diazoacetone, particularly in the field of the fluoride-induced aldol-type additions (Scheme 2, eq 2).…”

Basicity, acidity and hydrogen bonding

“…Basicity, acidity and hydrogen bonding 183 Thc difference in coupling constants betwcen the inethine proton and that derived from the acid in 6 snd 7 tends 10 confirm 0-protonation. In FSO,H-SbF,-SO, a t -60 "C neither this H-H coupling nor, indeed, the resonance of thc OH proton could be observed due to its rapid exchange with the solvent protons.…”