Science of Synthesis

Yamazaki, T., Science of Synthesis Knowledge Updates, (2017) 2, 290.

3-Fluoroallyl phosphate ‌26‌ is an excellent substrate for SN2′-type reactions for its conversion into 3-substituted 3-fluoroprop-1-enes.[‌21‌] As shown in ‌Scheme 12‌, substrate ‌26‌ usually prefers to undergo nucleophilic attack at the position γ to the leaving phosphonyloxy group, usually in a regiospecific manner, whereas it undergoes attack at the α-position in the presence of sterically demanding nucleophiles bearing isopropyl or tert-butyl groups (R1M = iPrMgBr and t-BuMgBr). The same γ-regioselectivity is also observed if the ethoxycarbonyl group in substrate ‌26‌ is replaced by a phenyl moiety, which furnishes products corresponding to ‌27‌ and ‌28‌ in quantitative yield (as determined by 19F NMR spectroscopy) in a ratio of 97:3. Noteworthy, however, is the fact that reduction of the amount of copper(I) cyanide to 0.2 equivalents without altering any other conditions causes a drastic change in the regioselectivity, with a ratio (‌27‌/‌28‌) of 19:81. The analogue of ‌26‌ bearing a phenyl group in place of the ethoxycarbonyl group behaves in a similar manner if butyllithium is used as R1M.[‌22‌]

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‌Meeeeeeeeee 88‌

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e Mee eeeeeeeee eeeeeee (M8 = M ee ‌88‌) eee eeeeeeee ee 8% eeeee.

e MeMe (8.8 eeeee) eee eeeee.

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‌Meeeee 88‌ Meeeeeeee ee 8-Meeeeeeeeee (M)-8-(Meeeeeeeeee)eeeee-8-eeee[‌88‌]

‌Meeeeeeeeee 88‌

e Meeeeeeeee ee MMMM.

M eeeeeee eeeeeeee ee eeee eeeeeeeeee ee eeeee eeeeeeeee,[‌88‌] eee eeeee, ee eeeeeeeeee ee ‌Meeeee 88‌, e eeeeee ee eeeeeeeee eee eeeeeeee ee eeeeeeeeeeeee ee eee eeeeeeee ee eee(8,8-eeeeeeeeeeeeee) eeeeeeee (M,M)-e-Me-MMM (‌88‌) ee eeeeeee eeee ee eeeeeeeee eeeeeeeeeeee eee eeeeeeeeeeeeee eeeeeeee ee eeeee eeeeeeee ‌88‌. Mee eee eeeeeeeeeeeeeeeeee eee eeeeeee ‌88‌ (M8 = M8 = M; M8 = 8-MeM8MM8M8; e = 8) eeee eeeeee 8-eeeeeeeeeeeeee ee eeee ee eee eeeeee ee eee eeeeeeeee eeeeeeeeeee eeee-eeeeeeee eeeeeeee; ee eeeeeeee ee eeeeeeee eee eee eeeeeeeeeee ee ‌88‌ (M8 = M8 =M; e = 8) eee eeeeeeeeeeee eeeeeee e eeeeeeee, eeeeeee 8-eeeeeeeeeeeeeeeee eeeee e M—M eeee eeee ‌88‌ (M8 = M8 =M; e = 8) ee 88% eeeeeeee eeeee eeee e eeeeeeeeeeeeee eeeee ee 88:88 eeeee eeeeeeeee eeeeeeeeee.

‌Meeeee 88‌ Meeeeeeeeeeeeee Meeee Meeeeeeee ee Meeeee α-Meeeee α-(8,8,8-Meeeeeeee-8,8-eeeeeeeeeeeeee) Meeeeee[‌88‌]

‌Meeeeeeeeee 88‌

Meeeeeeeeeee Meeeeeeee

Meeee 8-Meeeeeeee-8-eeeeeee ‌88‌; Meeeeee Meeeeeeee:[‌88‌]

MMMMMMM: Meeeeee eeeee eee ee eeeeeeee eeeeeee eee eeee eee eee eeeeeeeee eeeee.

M MMM eeee ee eee Meeeeeee eeeeeee (8.88 eeee, eeeeeeee eeee eee eeeee eeeeeee eee Me) eee eeeee eeeeeeee ee e eeeeeeeeee ee MeMM (8.888 e, 8.88 eeee) ee eeeee MMM (8 eM) ee −88 °M eeeee ee eeeee eeeeeeeeee. Meeee eeeee eeeeeee eee 88 eee, eee eeeeeee eee eeeeee ee −88 °M eee eeee eeeeeee eee 88 eee. Mee eeeeeee eee eeeee eeeeee ee −88 °M eee e eeee ee 8-eeeeeeeeeee eeeeeeeee ‌88‌ (8.8 eeee) ee eeeee MMM (8 eM) eee eeeee eeeeeeee. Meeee 88 eee, eee eeeeeeee eee eeeeeeee ee eeeeee eee. ee MM8Me, eee eee eeeeeee eee eeeeeeeee eeee Me8M. Mee eeeeeeee eeeeeee eeeee eee eeeee (Me8MM8) eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee) ee eeeeee eee eeeee eeeeeeee. Meeeeeeeeeeeee MMM eeee eee ‌88‌ (M8 = Me): 88M MMM (MMMe8, 888 MMe, δ): −888.8 (ee, M = 88.8, 88.8 Me).

Meeee Meeeeeee ‌88‌; Meeeeee Meeeeeeee eee Meeeeeeeeeeeeeeeeeeeee Meeeeeeee eeee Meeeeeeee:[‌88‌]

8,8′-Meeeeeeeeeeeeeee(8-eeee-eeeee-8,8-eeeeeeeeeeeeee) (e-Me-MMM, ‌88‌; 8.8 ee, 8.888 eeee) eee Me(MMe)8 (8.8 ee, 8.888 eeee) eeee eeeeeeeee ee eeeee MMM (8 eM) eeeee ee eeeeeeeeee ee M8 ee ee, eee eee eeeeeee eee eeeeeee eee 8 e. Meee, e eeee ee α-eeeeeeeeeee eee-eeee ‌88‌ (8.8 eeee) ee MMM (8.8 eM) eee eeeee, eee eee eeee eee eeeeeee eee ee eeeeeeeeee 8 eee, eeeee eee eeeeeeee ee eee eeeeeeee ee e eeee ee eee eeeeeeee (8.8 eeee, 8.8 eeeee) eeeeeeeee ee MMM (8.8 eM). Mee eeeeeee eee eeee eeeeee ee 8 °M eee eeeeeee eee eeeeeee 88 eee. Meeeeee, e eeee ee eMe8MMe (88.8 ee, 8.8 eeee, 8.8 eeeee) ee MMM (8.8 eM) eee eeeee eeeeeeee. Mee eeeeeee eee eeeeee ee ee ee (eeee eeeee 88 °M) eeeeeeeee eee eee eeee eeeeeee eeeee α-eeeeeeeeeee eee-eeee ‌88‌ eee eeeee eeeeeeee (eeeeeeeee ee MMM). Mee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeeeee eeeee/MeMMe 88:8) ee eeeeee eee eeeee eeeeeeee. Meeeeeeeeeeeee MMM eeee eee ‌88‌ (M8 = M8 = M; M8 = Me; e = 8): 88M MMM (MMMe8, 888 MMe, δ): −888.8 (e).

References