Allene Epoxidation. Highly functionalized tetrahydrofurans and tetrahydropyrans from the oxidative cyclization of allenic alcohols.

Catalytic Asymmetric Synthesis of Chiral Phosphanes

“…Computational studies reveal strikingly similar transistion states for the three classes of nucleophile. The angle of nucleophilic attack (Nu‐C1‐O1: 158° ( 8 ), 168° ( 10 ), 161° ( 13 ), 170° ( 15 ); Scheme ) reflects a degree of cationic character at C1 15. For all nucleophiles in this study, the C1O1 bond lengthens, the O1C2 bond shortens, and the C2O2 bond lengthens upon nucleophilic attack of the SDE, although the epoxide opening occurs at different rates (compare 8 , 10 , 13 , and 15 , Table 3).…”

Synthesis of unusually strained spiroheterocyclic ring systems and their exploits in synthesis

“…40,41 Thus, oxidation of allenic alcohols 65 containing a one or two carbon atom tether yielded furanones 64 that proceeded through attack at the distal epoxide C-O bond by the pendant alcohol. However, when the tether was extended to three or four carbon atoms, nucleophilic addition favored the proximal epoxide C-O bond to form tetrahydrofurans 66 and tetrahydropyrans 67 , respectively.…”

Oxidative cyclization in the synthesis of 5‐ and 6‐membered N,O‐heterocycles

“…The oxidation of ␤-allenyl alcohols 428 by dimethyldioxirane leads to functionalized tetrahydropyran-3-ones 429 in high yield, presumably via a spiro-dioxide derivative [217]. Under acidic conditions, a competitive cyclization leads to the simple pyran-3-one 427.…”