Allene epoxidation. Oxidative cyclizations of allenyl alcohols.1

Dioxiranes: a half-century journey

“…could oxidize 278, 280, 282 and 284 in a facile manner to 279, 281, 283 and 285 in 96, 10, 98 and 80% yield, respectively. 234 The efficiency of oxidation was found to increase from naphthalene (282) to phenanthrene (278), whereas a drastic drop in oxidation was observed for the oxidation of anthracene (284) to pyrene (280). NMR studies during the oxidation of 280 at −20 °C confirmed the decomposition of 10 to 64 (∼6% after 48 h), which was proposed to proceed by a radical process (Scheme 64).…”

“…279 Furthermore, when an allenic alcohol 441 was treated with a cold solution of 9, cyclized hydroxy-tetrahydro furanone 442 was isolated in 55% yield (Scheme 94b). 280,281 However, in the presence of pTSA (0.5 equiv. ), tetrahydrofuran 443 was formed as the major product (Scheme 94c).…”

“…106,[224][225][226][227] Jeyaraman and Murray employed 9 (in situ) for the oxidation of arenes in the presence of a PTC at pH ∼ 7.5-8.5 (Scheme 61). 228 Phenanthrene (278), pyrene (280) and naphthalene (282) produced epoxy products, whereas anthracene (284) gave oxidation product 9,10-anthraquinone (285). 228 Furthermore, in 1989, Agarwal et al employed 9 (stoichiometric) to prepare epoxides of various polyaromatic compounds.…”

“…53,280 When gem-disubstituted alcohol 444 was subjected to the same reaction conditions, triol 445 was formed in 89% yield (Scheme 94d). 280 Similarly, allenyl carboxylic acids were successfully converted into highly functionalized lactones derivatives in up to 87% yield. 282 In 1992, the Crandall group studied the epoxidation of cumulene 446 using 9 that led to cyclopropenone 447 and 448.…”

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.…”