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27.14.4.2.2 Method 2: Conversion into 2-(Trialkylsiloxy)isoxazolidines

DOI: 10.1055/sos-SD-027-00486

Jie Jack Li, Science of Synthesis, (200427597.

1,3-Dipolar cycloaddition involving silyl nitronates is the most important application of silyl nitronates in organic synthesis. [3+2] Cycloaddition of silyl nitronate 74 with alkene 73 (in almost all cases terminal alkenes are used, although there are a few exceptions[‌46‌]) proceeds either inter- or intramolecularly to afford 2-(trialkylsiloxy)isoxazolidine 75 (Scheme 20).[‌65‌] Isoxazolidine 75 is then converted into the corresponding 4,5-dihydroisoxazole 76 on treatment with either fluoride or acid by elimination of trialkylsilanol. Therefore, silyl nitronates are regarded as synthetic equivalents of nitrile oxides with regard to their [3+2] cycloadditions with alkenes. However, silyl nitronates are not as reactive as the corresponding nitrile oxides and the reactions generally take longer. For example, the [3+2] cycloaddition of acrylonitrile (77) and 1-(trimethylsilyl-aci-nitro)methane, derived in situ from nitromethane, takes 18 hours to give 2-(trimethylsiloxy)isoxazolidine-5-carbonitrile (78; Scheme 20).[‌57‌] It is not uncommon for such reactions to take as long as 3 days at room temperature to go to completion.

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Meeeeeeeee [8+8] eeeeeeeeeeeee eeeee eeeee eeeeeeeeee eee eeee eeeeeeee eeee eeeeeee-88,8-eeeeee eeeeeeeeeee ee eeeeee eeeeeeeeeee.[‌88‌,‌88‌] Me eeeeeee eeee,[‌88‌] eee eeeeee eeeeee ee γ-eeeeee α,β-eeeeeeeeeee eeeeee 88, eee eee eeeee eeeeeeeee ee eeeeeeeee ee eeee eeee 8-eeeeeeeeeeee. Mee [8+8] eeeeeeeeeeeee eee eeeeee ee ee eeeeeeeeeeeee eee eeeeee eeeeeeeeeeeeeeeeee. Mee eeeeee, (M)-M-(eeeeeeeeeeeeeee)eeeeeeeeeeeee 88, ee eeeeee ee 88% eeeee eeee 88:8 eeeeeeeeeeeeeeeeeeee (Meeeee 88).

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Meeeee 88 Meeeeeeeeeeeee 8,8-Meeeeee Meeeeeeeeeeee ee e Meeee Meeeeeeee Meeeeee eeee e Meeee Meeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

8-(Meeeeeeeeeeeeee)eeeeeeeeeeeee-8-eeeeeeeeeeee (88):[‌88‌]

MMMMMMM: Meeeeeeeeeee ee eeeeeeeee eee e eeeee- eee eeee-eeeeeeeee eeeeeeeee, eee ee ee eee, eeee, eee eeeeeeeeeee eeeee eeeeeeee.

Me eeeeeeeeeeeee (88; 88.8e, 8.8eee), Me8M (88.8e, 8.8eee), eee MMMMe (88.8e, 8.8eee) ee eeeeeee (888eM) (MMMMMMM: eeeeeeeeee) eee eeeee MeMM8 (88.8e, 8.8eee) eeeeeeee ee ee eeee eeeeeeee. Meeee 88e, eee eeee eee eeeeeeee, eeeeeeeeeeee, eee eeeeeeeee ee eeeee (8888°M/8.8Meee) ee eeee eee eeeeeee; eeeee: 88%.

(8eM,8M)-8-(8-Meeeeeeeeeeeee)-8,8-eeeeeeee-8e,8,8,8-eeeeeeeeee-8M-eeeeee[8,8-e]eeeeeeeee (88):[‌88‌]

Me e eeee ee [8-(eeeeeeeee)-8-(8-eeeeeeeeee)eeeeee]eeeeeeeeeeeeeeeeeee (88; 888ee, 8.8eeee) ee MM8Me8 (8eM) eee eeeee Me8M (8.88eM, 8.8 eeeee) eeeeeeee ee MMMMe (8.8eM, 8.8 eeeee) eeeee eee MM8Me8 eeeeeeee ee eee eeeeeee. Mee eeeeeeeee eeee eee eeeeeee ee 88°M eee 88e eee eeee eeeeeeeeeeee ee eeeee. Mee eeeeeee eee eeeee ee ee MM8Me8 (88eM) eee eeeeeeee ee eeeeeeeeeeeeee (eeeeee eee, eeeeee/MeMMe 88:8) ee eeeeee eee eeeeeee; eeeee: 88%; 8:8 ee.

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