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43.8.2.3.1 Method 1: Alk-2-ynes by Base-Catalyzed Rearrangement of Alk-1-ynes

DOI: 10.1055/sos-SD-043-00415

Krueger, A.Science of Synthesis, (200843500.

One of the most important preparative variations of the base-catalyzed rearrangements is the transformation of terminal alkynes 96 into their methylalkynes 97 by rearrangement (Scheme 45).[‌148‌‌153‌] In some cases this reaction leads to the alk-2-nye in almost quantitative yield. The choice of the base and solvent has an important influence on the outcome of the reaction. Milder bases lead to good to excellent yields of alk-2-ynes. Higher temperatures and stronger bases favor the formation of further internal alkynes or conjugated dienes. Typically, alkoxides and amides are used as the base. Prominent examples include potassium tert-butoxide, sodium amide, or potassium 3-aminopropylamide (KAPA). Solvents include dimethyl sulfoxide, liquid ammonia, alcohols, ethylenediamine, etc.

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Mee-8-eee Mee-8-eee Meeeeeeeee Meeeee (%) Mee
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eee-8-eee eee-8-eee e-MeMM, MMMM, ee 88 [‌888‌]
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eee-8-eee eee-8-eee 8M MMM, MeMM 88 [‌888‌]
eee-8-eee eee-8-eee MeMM8, MMMM, 8888°M, 88e 88 [‌888‌]
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Mee-8-eee Mee-8-eee Meeeeeeeee Meeee (%) Mee
MMMMM8MMe8 MeMMMMe8 e-MeMM, MMMM, 8888°M 88 [‌888‌]
MMMMM8MMe8 MeMMMMe8 MMM8/eeeeeee, eeee eeeeeee 88 [‌888‌]
MMMMM8MMe8 MeMMMMe8 MMM8/eeeeeee, eeee eeeeeee 88 [‌888‌]
MeMMMMe8 MMM8/eeeeeee, eeee eeeeeee 88e [‌888‌]
MMM(MM8)8MM MeMM(MM8)8MM e-MeMM, MMMM, 8888°M 88 [‌888‌]
8. 88% ee M8MM8, 88°M, 8e
8. 88% ee M8MM8, 88°M, 8e
88e [‌888‌]
MMM(MM8)8MM8M MeMM(MM8)8MM8M 88M MMM, 888°M, 8e 88 [‌888‌]
MMM(MM8)8MM8M MeMM(MM8)8MM8M 8M MMM, eeeeeeee eeeeee, 888°M, 8e 88 [‌888‌]
MMMMM8MMe MeMMMMe MeMMe, eee MM8, 88°M 88 [‌888‌]
MMMMM8MMe MeMMMMe MMM, MMM, 88°M, 8e 88 [‌888‌]
MMMMM8M(e-Me) MeMMM(e-Me) MMM, MMM, 88°M, 8e 88 [‌888‌]
MMMMM8M(MM8)88Me MeMMM(MM8)88Me MMM, MMM, 88°M, 8e 88 [‌888‌]
MMM, MMM, 88°M, 88e 88 [‌888‌]
MMMMM8MeMe MeMMMeMe MMM, MMM, 88°M, 8e 88 [‌888‌]
MMMMM8MeMe MeMMMeMe 8.8M MeMMe, MeMM, 88°M 88 [‌888‌]
MMMMM8MMe8 MeMMMMe8 e-MeMM, MMMM, 88°M, 8e 88 [‌888‌]
MMM, MeMM, 88°M, 8e eeeee [‌888‌]
MMM, MeMM, 88°M, 8e 88 [‌888‌]
MMM, MeMM, 88°M, 8e 88 [‌888‌]

e Meeeeeee eeee 88% eeeeee eee eeeeeeee.

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Mee-8-eeee 88; Meeeeee Meeeeeeee:[‌888‌]

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Mee-8-eeeee Meee (88):[‌888‌]

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Meee-8,8-eeeeeee eeee (8.8e, 88eeee) eee eeeeee eeee 88% ee M8MM8 ee 88°M eee 8e. Meeee eeeeeeeeeeeee, eeeeeeeeee eeee Me8M, eee eeeeeeeeeeeeeee (eeeeeeeee eeeee), eee eeeeeee eee eeeeeeee ee e eeeeeeeee eeeee; eeeee: 8.8e (88%); ee 8888°M.

8-(Meeeeeeeeeeeee)eeee-8-eee (888); Meeeeee Meeeeeeee:[‌888‌]

8-(Meeeeeeeeeeeee)eeee-8-eee (888; 8e, 88eeee) eee eeeeeee eeee eeeeee eeeeeeee MMM (88e, 888eeee) ee MMM (88eM) ee 88°M. Meeee 88eee, eee eeeeeee eeeeeeee eee eeeeeeeeeeeeee eeeeeeeeeee, eeeee eee eeeeeeeeeeee eeeeee eee eeeeeeeeeee eeeee 88e (MM eeeeeee). Meeee eeeeeeee eeee M8M eee eeeeeeeeee eeee eeeeeeeee eeeee, eee eeeeeee eee eeeeeeee ee eeeeeeeeeeee eeeeeeeeeeee; eeeee: 8.88e (88%); eM88 8.8888.

References