Stereospecific conversion of epoxides into olefins

Half rotations leading to retention of stereochemistry in epoxide ring opening by selenocyanate ion: Insights from DFT modeling

“…Deoxygenation of stilbene oxide by selenocyanate ion has been done experimentally by Culvenor et al and based on the stereochemistry of the reaction obtained; Behan et al13 have suggested a possible mechanism as shown in Scheme . The detailed scheme of the reaction modeled at B3LYP/6‐31+G(d) level is given in Figure 1.…”

“…Similarly, potassium selenocyanate in aqueous methanolic solution reacts with trans ‐stilbene oxide to form trans‐ stilbene with a high degree of retention of stereochemistry (Scheme ) and is mechanistically interesting11, 12. Behan et al13 have suggested a possible mechanism for this reaction with two half rotations around CC bond and observed the formation of an episelenide intermediate. These are the minimum details available on the mechanism of the reaction and taking these clues, the reaction has been modeled to answer the following points: (i) mechanism of the reaction, (ii) the factors that control the stereochemistry of the reaction, (iii) possible mode of attack, (iv) transition states and intermediates, (v) half rotations, and (vi) decomposition of episelenide.…”

Total synthesis of xanthanolides

“…8 Attempts to reduce the epoxide in 50 to an alkene using SmI 2 21 or P 2 I 4 22 resulted in a complex mixture, but KSeCN successfully reduced the epoxide to give 5 in good yield (Scheme 10). 23 With the key intermediate in hand, we tried to convert 5 to…”

Effects of 3-Methylgibberellin Analogs on Gibberellin 3β-Hydroxylases and Plant Growth

“…This mixture was purified on a silica gel thin-layer plate developed with EtOAc-n-hexane (1 : 1, v/v) to give 3-oxo-GA 9 -Me (124mg, R r = 0.59-0.75) and GA 4 -Me (22mg, R r = 0. 22 Preparation of 2,3-Didehydro-3-methyl-GA 9 (2). Compound 25 (40 mg) was refluxed with phosphoryl chloride (140 Jil) in dry pyridine (3Aml) to give a dark brown oil.…”