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16.2.4.2.2 Dibenzo[b,e][1,4]dioxins from the Diels–Alder Reactions of 1,4-Benzodioxin and Benzo[b]furo[3,4-e][1,4]dioxins

DOI: 10.1055/sos-SD-116-00505

Sakya, S. M.; Yang, J.Science of Synthesis Knowledge Updates, (20121232.

The DielsAlder reaction is a powerful approach to the synthesis of substituted dibenzo[b,e][1,4]dioxins in a single step. For example, the reaction of benzo[b]furo[3,4-e][1,4]dioxins 26 with thiolactone 27 (X=S) in the presence of a catalytic amount of ytterbium(III) trifluoromethanesulfonate gives thiolactone-substituted dibenzo[b,e][1,4]dioxins 28 and 29 in 2777% yield (Scheme 6).[‌26‌] Only ytterbium(III) trifluoromethanesulfonate catalysis gives dehydrated products directly and the major product has been determined to be that with the small (R3) substituent ortho to the carbonyl group (compound 29).[‌26‌] The DielsAlder reaction has also been performed without a catalyst, but this requires acid- or base-catalyzed dehydration of the formed intermediates 30 to give the benzo[b,e][1,4]dioxins 31.[‌27‌,‌28‌]

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Meeeeeeeeee 8

M8 M8 M8 M Meeee (%) Mee
88 88
M Me Me M 88 [‌88‌]
M Me Me M 88 88 [‌88‌]
M (MM8)8Me Me M 88 88 [‌88‌]
MMe (MM8)8Me Me M 88 88 [‌88‌]

M8 M8 M8 M8 Meeee (%) Mee
88 88
Me Me M MM 88 88 [‌88‌]
Me Me MM8Me MM8Me 88 88 [‌88‌]
Me Me M MM 88 88 [‌88‌]

Mee MeeeeMeeee eeeeeeee eee eeee eeee eeeeeeeeeeee eeeeeee 8,8-eeeeeeeeeee (8) eee 8,8-eeeeeeeeeeeee[e]eeeee (88) ee eeeeeeeee eeeeeee, ee eeee eeeeeeeeeee eeeeeee[e,e][8,8]eeeeee 88 ee eee eeeee eeeeeee (Meeeee 8).[‌88‌] Meeee eee eeeeeeee eeeeeeeeee, eee eeeeeee MeeeeMeeee eeeeee 88 ee eeeeeeee eeee ee e eeeee eeeeeee, eee ee eeeee eeeeeeeeeee ee eee eeeeeeeeee eeeeee eee eeeeeeeeeeeee eeee eeeeeee eeee eeeeeeeee (eeeeeeee eee ee eee eeeeeeee ee eee eeee eeeeee), ee eeee eee eeeeee eeeeeee.[‌88‌] Meee ee ee eeeeeeee ee eeeeeee eeeeeee ee 8,8-eeeeeeeeeee eeeeeeeeeeeee ee MeeeeMeeee eeeeeeeee eeee eeeeeee eeeeee, eeeee eee eeeee ee ee ee eeeeeeeeee.[‌88‌]

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Meeeeeeeeeee Meeeeeeee

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8,88-Meeeeeeeeeeee[e]eeeeeee[e,e][8,8]eeeeee (88):[‌88‌]

Me eeee-eeeee eeeee eeeeeeee eeee e eeeeeeee eeeeeee eee eee eeeeeee eeee 8,8-eeeeeeeeeee (8; 888ee, 8.88eeee) eee 8,8-eeeeeeeeeeeee[e]eeeee (88; 888ee, 8.88eeee) ee eeeee eeeeeee (8eM). Mee eeeeeee eee eeeeee ee 888°M eee 88e eeeee eeeee eeee ee eee eeeeee ee ee, eeeeeeee eeee eeeeee eee, eee eeee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee/MeMMe 8:8) ee eeee eee eeeeeee ee e eeeee eeeee; eeeee: 888ee (88%); ee 888888°M; eeeeeeee eeee eeeee eeeeeee ee eee eeeeeeeeeeee 88; eeeee: 8%.

References


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