- Domino inverse electron-demand Diels-Alder/cyclopropanation reaction of diazines catalyzed by a bidentate lewis acid
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A domino inverse electron-demand Diels-Alder (IEDDA)/cyclopropanation reaction of diazines was discovered by applying electron-rich furans in the bidentate Lewis acid catalyzed IEDDA reaction. This process produces benzonorcaradienes in excellent yields with a low loading of a bidentate Lewis acid catalyst of 2 to 5 mol %. We demonstrate the broad applicability by 20 examples with different dienophiles and a variety of dienes. A detailed mechanism is proposed supported by DFT calculations.
- Kessler, Simon N.,Neuburger, Markus,Wegner, Hermann A.
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supporting information
p. 17885 - 17888,4
(2020/09/16)
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- A stereospecific '2-aza-divinylcyclopropane' rearrangement
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The stereochemical course of the thermal 2-aza-Cope rearrangement of the optically pure acyl azide (-)-(1S)-5 was investigated by determination of the absolute configuration of the rearrangement product (1R,8S)-9. The reaction proceeds by a sequence of stereospecific steps from 5 to an equilibrating mixture of exo- and endo-isocyanates 6 and 7. The endo-isomer 7 undergoes Cope rearrangement to the putative intermediate 8, which is trapped and characterized as the adduct 9b of butan-1-ol. The absolute configuration of 9b was determined by its reduction to the amide 20, and determination of the X-ray structure of the N-camphanoylamide 21 derived from camphanic acid of known absolute configuration.
- Mueller, Paul,Toujas, Jean-Louis,Bernardinelli, Gerald
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p. 1525 - 1534
(2007/10/03)
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- Conversion of Benzo- and Naphthonorcaradien-7-yl to Benzo- and Naphthotropyl Radicals
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Thermal decompositions of tert-butyl 2,3-benzonorcaradiene-7-percarboxylate (7), tert-butyl 2,3-(2',3'-naphtho)norcaradiene-7-percarboxylate (8), bis(2,3-benzonorcaradiene-7-carbonyl) peroxide (9), and bis peroxide (10) have been studied with particular attention paid to the hydrocarbon products, 2,3-benzonorcaradiene (11) and 1,2-benzotropilidene (12) from 7 and 9, and 2,3-(2',3'-naphtho)norcaradiene (14) and 1,2-(2',3'-naphtho)tropilidene (15) from 8 and 10.The variation of product ratio with solvent from 7 and 8 suggests that the intermediate benzo- and naphthonorcaradien-7-yl radicals competitively abstract a hydrogen atom or undergo ring opening to the corresponding tropyl radical.A similar study of 9 and 10 suggests that there is an additional, polar component to formation of seven-membered ring products 12 and 15.Since the hydrocarbon products are free radical in origin, it is suggested that the intermediates, whether highly polarized species or free cations, must revert back to free radicals before giving these products.It is further suggested that the greater degree of ring opening from the diacyl peroxides, 9 and 10, is due to the greater allowedness of the ring opening of the norcaradienyl type cations relative to the corresponding radicals.It is also demonstrated that benzonorcaradienyl intermediates undergo ring opening more readily than the corresponding naphthonorcaradienyl intermediates.
- Pomerantz, Martin,Dassanayake, N. L.
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p. 678 - 682
(2007/10/02)
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