Navigation

0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via
27.17.4.2.2 Method 2: Synthesis of Alkenes

DOI: 10.1055/sos-SD-027-00576

Kim, S.; Yoon, J.-Y.Science of Synthesis, (200427707.

The interaction of the tosylhydrazone of an alkyl ketone with a base in a protic or an aprotic solvent to provide an alkene is called the BamfordStevens reaction.[‌133‌,‌143‌,‌144‌] It proceeds through a diazo compound, followed by the formation of two possible intermediates, a carbene or a carbocation. For example, in aprotic solvents the diazo compound 155 loses nitrogen to generate the carbene 156, which undergoes hydrogen migration to afford 3,3-dimethylbut-1-ene, and insertion to give 1,1,2-trimethylcyclopropane. In a protic solvent, however, the diazo compound is protonated to give the diazonium ion 157, which loses nitrogen to give the carbocation 158, that in turn may undergo elimination to give 2,3-dimethylbut-2-ene (Scheme 36).[‌145‌] Typical procedures for the BamfordStevens reaction involve the use of sodium hydride in ethylene glycol, or in diglyme, but require rather severe conditions. Tosyl hydrazones also undergo the Shapiro reaction. In an illustration of this procedure the monoanion 159, formed by deprotonation of the corresponding tosyl hydrazone with an alkyllithium, can be further deprotonated by the alkyllithium at 78°C to give the dianion 160, which decomposes at 025°C to give 3,3-dimethylbut-1-ene, via the vinyl anion 161 (Scheme 36).[‌146‌,‌147‌] This reaction is regiospecific, favoring the less-substituted alkene when there is a choice of products; for example, the tosylhydrazone 162 gives 2-methylcyclohexene as the major product (>98%) and only a minor amount of its isomer 1-methylcyclohexene (<2%). The Shapiro reaction is more conveniently performed than the BamfordStevens equivalent and it can be used for the preparation of born-2-ene (163) from the tosylhydrazone of camphor (Scheme 36).[‌148‌]

Meeeee 88 Meeeeee eeee Meeeeeeeeeeeeee[‌888‌,‌888‌‌888‌]

M-Meeeeeeeeeeeeeeeeeeeeeeee eeeeee ee ee eeeeeeeee eeeeeeee ee Meeeeee-eeee eeeeeeeeeee eeeeeeeee, eee eee ee eeee ee eeeeeeeeeeeeee eeeeeeeeeee ee eeeeee eeeeeeeee. Meeee eeeeeeee eeee eeeeee eeeeeee eeeeeeeeeeeeeeee ee eeeeeee eee eeeeeeeeeeeee/eeeeeeeeee eeee,[‌888‌] eee eeeeeee eee eeee ee eeeeeeeeeeee eeeeeeee eeeee e eeeeeeeee eeeeee ee e eeeeeee eeeee.[‌888‌] Mee eeeeeeeee eeeeeeeee eee eeeeee eeeee- eee eeeeeeeeeeeeeee, eeeeeeeee e eeeeeeee eeeeeee eeeeeeeeeeee; eeee, eeeeeeeee ee eeeeeeeeeeeeeeeeeeee 888 ee eeeeeee eeeee eeee e eeeeeeeee eeeeee ee eeeeeee eeeeeeeeeeeeeeee ee 88°M eee 8 eeee eeee eee ee 8°M eee 8 eeeee eeeeeee ee eee eeeeeeeee ee eeeeeee eee eeeeeeee ee eeee eee eeeeee eeee eee-eeeeeee 888 ee eeee eeeeee. Mee eeeeee ee eeeeeee eeeeeeeeeeeeeeee eee ee eeeeeee ee 8.88 eeeeeeeeee eeeeeee eeeeeeeee eee eeeeee eee eee eee/eeeee eeeeee ee eee eeeeee eeeeeeee. Meeeeee 8,8,8,8-eeeeeeeeeeeeeeeeeeeee ee eeeeeee eeeeeeeee, eee eeeeeee eeeeeeeeeeee eee eeeeeee eeeeeeeeeeeeeeeeeeeeee eeee eeee eeeeeeeeeeee eeeeeee (Meeeee 88).[‌888‌]

Meeeee 88 Meeeeee eeee M-Meeeeeeeeeeeeeeeeeee[‌888‌,‌888‌]

Meeeeeeeeee 88

M8 M8 Meeeeee Meeee (eeeee) Meeeeeeeeee/Meee Meeeeeeeeeeeeeee Meeee (eee/eeeee) Meeee (%) ee 888 Mee
(MM8)8Me Me MMM (8.8) 88 ee 8/8.8 88.8:8.8 88 [‌888‌]
(MM8)8Me Me MMM (8.88) 8/8 88.8:8.8 88 [‌888‌]
(MM8)8Me Me MeMMM (8.8) 8/8 88.8:8.8 88 [‌888‌]
(MM8)8Me Me MeMMe8 (8.8) 8/8 88:8 88 [‌888‌]
Me (MM8)8Me MMM (8.8) 8/8 88:8 88.8:8.8 88 [‌888‌]
(MM8)8Me Me MMM (8.8) 8/8 88.8:8.8 88.8:8.8 88 [‌888‌]

Me eeeeeee eeeee e eeee eee eee ee eeeeeeee ee eee eee, eee eeeeeeee, eee eeeeeeeeeeeeeeeeeee 888 ee eeeeeeeee eeee eee eeeeeeeeeee 888 eeeeee ee eeeeeee ee ee Meeeeee eee 8e ee 888°M (Meeeee 88).[‌888‌] Meee, eeeeeee, eee eeeeeee eeeeeeeeeee eeeeeeee eeeeeeeeeeeeeeee eee e eeeeeee eeeeeeeeeeee.

Meeeee 88 Meeeeeeee ee Meeeeeeeeeeeeee Meeeeeeeee-8-ee Meeee[‌888‌]

Meeeeeeeeeee Meeeeeeee

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

Meeeeeeee eeee (Meeeeee; Meeeee, Meeeeee Meeeeeeee, Meeeeeeeee Meeeee MM), Meeeeeeee (8888), e888, eeee eeeeeeeeee eeee Meee Meeee&Meee, Mee.

Meeeeee eeeeeeeeeeeeee (88e, 8.88eee) eee Me8M (888eM) ee e eee 8-M, eeeee-eeeeee eeeee eeee eeeeeeeee eeee eeeeeeee, eee eee eeeee eee eeeeeeee ee e eeeee eeee, eee eee eeeeeeee eeeeeeeeeeee eeeeeee. 8.8M MeMe ee Me8M (888eM, 8.88eee) eee eeeee eeeeee 8e ee eee eeeeeee eeee, eee eeeeeeee eee eeeeeeeee eee 8 ee 8e, eeeeee eeeee eeee eee eeeeeee eeeeeeeee e eeee eee-eeeeee eeeee. M eeeee eeeeee ee M8M eee eeeeeeeeee ee eeeeeee eee eeeeee MeMe, eee eeee eeee M8M (888eM) eee eeeee. Mee eeeeee eeee eeeeeeeee, eee eee eeeeeee eeeee eee eeeeee eeee M8M, eee eeeee. Mee eeeeeee eee eeeeeee ee eeeeeeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeeee; eeeee: 8.88.8e (8888%); ee 888888°M.

Meeeeee 888 eee eee Meeeeeeeeeeee ee M-Meeeeeeeeeeeeeeeeeee; Meeeeee Meeeeeeee:[‌888‌]

Meeeeee eeeeeeee 8.8M MMM ee Me8M/eeeeee (8.88.8eM) eee eeeee ee eee M-eeeeeeeeeeeeeeeeeee (8.8eeee) ee Me8M ee 8°M eeeee eeeee. Meeeeeeee ee M8 eee eeeeeeee eee eee eeeeeee eee eeeeeee ee 88 ee 88°M eee eeeeeee eeeee, eeeeee ee eee eeeeeee eeee Me8M (8eM) eee eeeeee eeee e eeeeeeeeee eeeeee eeeeeeeeee 8M MMe ee M8M (88eM). Mee eeeeeee eeeee eee eeeeeeeee eeee Me8M (8×88eM). Mee eeeeeee eeeeee eeee eeeeeeee, eeeeee eeee eeeee (88eM), eee eeeee (Me8MM8). Meeeeeeeeeeee ee eeeeeeee eee eeeeeeeeeeee ee eee eeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee) eeeeeeee eee eeeeee; eeeee: 8888%.

References


Cookie-Einstellungen