Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• suitably substituted aminocyclopropane derivatives [44][45][46]. In 2014, Hyland et al. disclosed the Overman rearrangement [47] of cyclopropenylcarbinyl trichloroacetimidates [48]. The optimal conditions for the generation of imidates 12a–i involved treatment of secondary cyclopropenylcarbinols with

• the N-acylamino group explained the modest face selectivity of hydrogen addition which preferentially occurred on the face of the olefin opposite to the N-chloroacetylamino substituent (Scheme 13) [48]. 3,3-Disubstituted cyclopropenylcarbinols could not be used as substrates in the Overman

• rearrangement. This limitation of the substrate scope is due to the instability of the corresponding trichloroacetimidates. Thus cyclopropenylcarbinols 20a–c possessing gem-dimethyl substitution at C3 were converted to imidates 21a–c but upon treatment with silica gel (CH2Cl2, −10 °C), those latter compounds

Efficient carbon-Ferrier rearrangement on glycals mediated by ceric ammonium nitrate: Application to the synthesis of 2-deoxy-2-amino-C-glycoside

• Alafia A. Ansari,
• Y. Suman Reddy and
• Yashwant D. Vankar

Beilstein J. Org. Chem. 2014, 10, 300–306, doi:10.3762/bjoc.10.27

• -glycosides; carbon-Ferrier rearrangement; ceric ammonium nitrate; 2-deoxy-2-aminoglycosides; Overman rearrangement; Introduction The growing significance of C-glycosides can be attributed to their potential use as inhibitors of carbohydrate-processing enzymes [1][2][3], their extraordinary stability

• crude form was heated under reflux in xylene, to afford the single isomer 10 in 72% yield by an Overman rearrangement [61][62][63]. The trichloroacetamide group was hydrolyzed by heating under reflux in 6 N HCl, and the obtained free amine was protected as a benzyloxycarbamate group by using benzyl

• chloroformate and Na2CO3. The protected amide 11 was obtained in 74% yield over 2 steps. The regioselectivity of the Overman rearrangement step was determined from the 1H NMR and COSY experiments of compound 11. These experiments showed that the anomeric proton (H-1) at δ 4.40 correlated with the H-2 proton at

Highly efficient gold(I)-catalyzed Overman rearrangement in water

• Dong Xing and
• Dan Yang

Beilstein J. Org. Chem. 2011, 7, 781–785, doi:10.3762/bjoc.7.88

• Dong Xing Dan Yang Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China 10.3762/bjoc.7.88 Abstract A highly efficient gold(I)-catalyzed Overman rearrangement of allylic trichloroacetimidates to allylic trichloroacetamides in water is reported. With this

• environmentally benign and scalable protocol, a series of C3-alkyl substituted allylic trichloroacetamides were synthesized in good to high yields. Keywords: allylic trichloroacetamides; allylic trichloroacetimidate; gold(I) chloride; Overman rearrangement; water; Introduction The aza-Claisen rearrangement of

• allylic trichloroacetimidates to allylic trichloroacetamides (Overman rearrangement) is a powerful and attractive strategy for the synthesis of allylic amines from readily available allylic alcohols [1][2]. This transformation can be conducted thermally at high temperatures or by transition metal