High Temperature Bromination. Part 12: Bromination of 7-Oxabenzonorbornadiene: Synthesis of 2,3-Dibromo-7-oxabenzonorbornadiene

Functionalization of oxabenzonorbornadiene: Manganese(III)‐mediated oxidative addition of dimedone

“…In the case of exo orientation of these protons, a high value of J 1,2 and J 3,4 , 3.5-5.0 Hz, would be expected. [7,8] Furthermore, 2 resonance signals in the 13 C-NMR spectrum appearing at 196.7 and 173.8 ppm clearly indicate that one of the carbonyl groups exists in its enol form. [9] Otherwise, the resonance frequencies of the carbonyl groups would appear at higher than 200 ppm.…”

“…The formation of the rearranged products was not expected because 7-oxabenzonorbornadiene (3) mainly undergoes a ring-opening reaction upon treatment with electrophiles. [3,7] We assume that the initially formed cation undergoes Wagner-Meerwein type rearrangement, thus forming a new cation that is captured by the oxygen atom of the carbonyl group in 10 to form 12. To hinder the Wagner-Meerwein type rearrangement, we decided to run the same reaction in the presence of HCl so that the initially formed cation can be captured by the chloride ion present in the reaction media.…”

Highly diastereoselective synthesis of a novel functionalized benzocyclotrimer

“…26 The radical bromination of 4 with 1,2-dibromotetrachloroethane (DBTCE) furnished the trans-dibromide diastereomer 5 in high yields (85%) (Scheme 1). In order to obtain the alkenyl bromide 6 the dehydrobromination reaction with potassium tert-butoxide in THF was used, 26 to afford the desired product 6 in good yield (90%) (Scheme 1).…”

“…26 The radical bromination of 4 with 1,2-dibromotetrachloroethane (DBTCE) furnished the trans-dibromide diastereomer 5 in high yields (85%) (Scheme 1). In order to obtain the alkenyl bromide 6 the dehydrobromination reaction with potassium tert-butoxide in THF was used, 26 to afford the desired product 6 in good yield (90%) (Scheme 1). The latter was brominated under high temperature conditions, which ensures high yields of dibromination, with limited amounts of Meerwein rearrangement products, 26 to obtain alkenyl tribromides exo-7 and endo-7, in a ratio of 2:1 and 96% overall yield (Scheme 1).…”

“…In order to obtain the alkenyl bromide 6 the dehydrobromination reaction with potassium tert-butoxide in THF was used, 26 to afford the desired product 6 in good yield (90%) (Scheme 1). The latter was brominated under high temperature conditions, which ensures high yields of dibromination, with limited amounts of Meerwein rearrangement products, 26 to obtain alkenyl tribromides exo-7 and endo-7, in a ratio of 2:1 and 96% overall yield (Scheme 1). The mixture of diastereomers was dehydrobrominated with potassium tert-butoxide in THF, 26 to afford the alkenyldibromide 8 in good yield (93%) (Scheme 1).…”