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47.1.4.6.3 Variation 3: Elimination from Halohydrin Esters

DOI: 10.1055/sos-SD-047-00322

Kostikov, R. R.; Khlebnikov, A. F.; Sokolov, V. V.Science of Synthesis, (201047833.

For acyclic vic-halohydrin esters, which are easily available from halohydrins, reduction to alkenes usually proceeds faster and under milder conditions than for the respective halohydrins. The classical reducing agents for halohydrin esters are zinc, magnesium, or sodium metals or organolithium compounds, as well as sodium iodide (see also HoubenWeyl, Vol. 5/1b, p 204).[‌224‌‌227‌] Some newer reagents for stereoselective or even stereospecific reduction have been developed. Thus, aliphatic erythro-iodohydrin acetates 101 provide E-alkenes 102 upon treatment with titanium(IV) chloride in the presence of allyltrimethylsilane, whereas the corresponding threo-isomers afford Z-alkenes exclusively (Scheme 41).[‌228‌] This protocol can also be applied to iodohydrin alkyl and silyl ethers. The photoinduced reduction by samarium(II) iodide of chlorohydrin acetates 103 with two aliphatic substituents provides Z-alkenes 104, but in the case of styrenes the E-isomers are formed exclusively. Since for this reaction a radical mechanism has been proposed, the configuration of the starting chlorohydrin has no importance (Scheme 42).[‌229‌]

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Meeeeeeeeee 88

M8 M8 Meeee (eeeeeee/eeeee) eee 888 Meeee (M/M) eee 888 Meeee (%) Mee
(MM8)8Me (MM8)8Me >88:8 88:8 88 [‌888‌]
(MM8)8Me (MM8)8Me <8:88 8:88 88 [‌888‌]
(MM8)8Me Me >88:8 >88:8 88 [‌888‌]
(MM8)8Me (MM8)8MMe >88:8 >88:8 88 [‌888‌]
(MM8)8Me (MM8)8MMe 8:88 8:88 88 [‌888‌]
(MM8)8Me (MM8)8Me 88:8 88:8 88 [‌888‌]
(MM8)8Me (MM8)8Me 8:88 88:88 88 [‌888‌]

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Meeeeeeeeee 88

M8 M8 Meeee (M/M) Meeee (%) Mee
(MM8)8Me Me >88:8 88 [‌888‌]
(MM8)8Me Me >88:8 88 [‌888‌]
(MM8)8Me e-Me 88:8 88 [‌888‌]
Me (MM8)8Me >88:8 88 [‌888‌]
Me Me 88:8 88 [‌888‌]
eMe (MM8)8Me 88:88 88 [‌888‌]

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(M)-Mee-8-eee [888, M8=(MM8)8Me; M8=Me]; Meeeeee Meeeeeeee:[‌888‌]

M eeee ee MeM8 (888ee, 8.8eeee) ee MMM (88eM) eee eeeee eeeeeeee, eeeee M8, ee e eeeeeee eeee ee eee M-eeeeeeeeee eeeeeeeeeeee 888 [M8=(MM8)8Me; M8=Me; 88ee, 8.8eeee] ee ee. Mee eeeeeee eee eeee eeeeee eeeee eeeeee eee 8e eee eeeeeeeeee eeee eeee 888-M eeeeeeeee eeeee. Meeee eeee eeee, eee eeeeeeee eee eeeeeeee eeee ee 8.8M MMe (88eM). Meeee eeeeee eee eeeeeeeeeeee ee eeeee-eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeee) eeeeeeee eee eeee eeeeeee; eeeee: 88ee (88%); Me 8.88 (eeeeee); 8M MMM (MMMe8, δ): 8.88 (e, M=8.8Me, 8M), 8.88 (e, M=8.8Me, 8M), 8.888.88 (e, 8M), 8.888.88 (e, 8M), 8.88 (ee, M=8.8, 8.8Me, 8M), 8.888.88 (e, 8M).

Meeeeeeeeeeeee Meeeeeeeeeee (888); Meeeeee Meeeeeeee:[‌888‌]

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