Rearrangement of .alpha.-bromocamphoric anhydride

Unknown Camphor: Regioselective Rearrangement under Acylation in a CF3SO3H/(CF3CO)2O System

“…Generally, the magnitude of the 3 J H,H coupling constant for protons with a cis configuration is much larger (7)(8)(9)(10)(11)(12) than that for protons with a trans orientation (2-6 Hz), and the presence of the appreciable long-range 4 J H,H coupling constant is specific for W-arranged protons. Generally, the magnitude of the 3 J H,H coupling constant for protons with a cis configuration is much larger (7)(8)(9)(10)(11)(12) than that for protons with a trans orientation (2-6 Hz), and the presence of the appreciable long-range 4 J H,H coupling constant is specific for W-arranged protons.…”

“…[5] The ability of camphor to undergo easy carbocationic transformations is one of its unique features. [7] However, synthetically useful methods for the stereo-and regioselective modification of camphor on the basis of skeletal rearrangements are limited to C9 and C10 sulfonation, [8,9] C9 bromination, [10] and transformation into 1-substituted camphenes under the action of phosphorus chlorides (e.g., PCl 3 /PCl 5 ), [11] trichloroacetic anhydride or trifluoromethanesulfonic anhydride (Scheme 1). [6] Its chemical modification is often accompanied by fascinating Wagner-Meerwein and Nametkin rearrangements, as well as by 2,6-hydride shifts, and leads to unpredictable products.…”

“…Therefore, camphor and its derivatives, relative to other simple organic molecules, have considerable potential for the creation of new molecular scaffolds. [7] However, synthetically useful methods for the stereo-and regioselective modification of camphor on the basis of skeletal rearrangements are limited to C9 and C10 sulfonation, [8,9] C9 bromination, [10] and transformation into 1-substituted camphenes under the action of phosphorus chlorides (e.g., PCl 3 /PCl 5 ), [11] trichloroacetic anhydride or trifluoromethanesulfonic anhydride (Scheme 1). [12,13] alkyl and hydride shifts and opens access to a new type of polyfunctional isoborneol.…”

Formation of synthetically useful camphor derivatives: mechanistic aspects

“…As shown in Scheme 2 this involves Wagner-Meenvein rearrangements, 3,2-exo-methyl shifts, and 6,2-hydride shifts and provides intermediates (e.g., 9b, lob) in which the original C(10) and C(9) methyl groups have become electrophilic exo-methylene groups. Thus to explain C(10) sulfonation of (+)-camphor (1) it is assumed that intermediate 9b reacts with SO3 or equivalent to provide an intermediate that can then undergo WagnerMeerwein rearrangement to regenerate the camphor framework and provide (+)-camphor-10-sulfonic acid (5). Similarly, to explain C(9) bromination of camphor, it is assumed that bromine reacts with intermediates l o b and ent-lob to provide brominated intermediates, which can then undergo WagnerMeenvein rearrangement to regenerate the camphor framework and provide a mixture of (+)-9-bromocamphor and (-)-9-bromocamphor (cf.…”

Methyl esters of camphoric and isocamphoric acids

“…From the rotations of the pure esters and that of the mixture it was calculated that the mixture contained 39% dimethyl /-isocamphorate and 61% dimethyl d-camphorate. From the "Data from Meyer, Lobo, and McCarty (5).…”