You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via47.1.4.7.1 Variation 1: Dehalogenation of Geminal Dihalides
Please login to access the full content or check if you have access via
Kostikov, R. R.; Khlebnikov, A. F.; Sokolov, V. V., Science of Synthesis, (2010) 47, 840.
The reductive dehalogenation of geminal dihalides cannot really be considered as a versatile synthetic route to alkenes. In the literature there are only a few examples of such reactions having a preparative importance. The reduction of gem-dihalides may proceed via either radical or carbenoid intermediates. Thus, photolysis of a number of (dihalomethyl)cycloalkanes in various solvents leads to complex mixtures containing alkenes with both unchanged and rearranged skeletons.[253] The carbenoids formed from gem-dibromides 116 and butyllithium–diethyl ether rearrange to alkenes 117 with acceptable yields (Scheme 46).[254] For simple alkenes, this reaction has a synthetic value only in the case of terminal gem-dibromides, whereas from internal gem-dibromides, mixtures of regio- and stereoisomers are formed. Terminal gem-dichlorides under the same conditions provide alkynyllithium compounds instead of alkenes. The reductive rearrangement of 2-alkyl-1,1-dibromocyclobutanes 118 upon treatment with methyllithium at −78°C affords the alkylidenecyclopropanes 119 in good yields (Scheme 47).[255]
Meeeee 88 Meeeeeee Meeeeee eeee eee-Meeeeeeeeeeeee[888]
Meeeee 88 Meeeeeeeeeeeeeeeeeeeeee eeee 8-Meeee-8,8-eeeeeeeeeeeeeeeeeee[888]
Meeeeeeeeeee Meeeeeeee
8-Meeeeeeeeeeeeeeee (888, M8 = MM8Me); Meeeeee Meeeeeeee:[888]
Me e eeeeeee eeee ee (8,8-eeeeeeeeeeeee)eeeeeeeeeee (888, M8 = MM8Me; 8.8 e, 88 eeee) ee Me8M (88 eM), eeeeeeeee ee −88°M, eee eeeee e 8.8 M eeee ee MeMe ee Me8M (88 eM, 88 eeee) ee −88 ee −88°M eeee e eeeeee ee 8 e eeeee e M8 eeeeeeeeee. Mee eeeeeeee eee eeeeeeee eeee 8 M M8MM8 (88 eM), eee eeeeeee eeeee eee eeeeeeeee eeee Me8M (8 × 88 eM), eee eee eeeeeeee eeeeeee eeeeee eeee eeeee (MeMM8), eee eeee eeeeeeeeeeee. Mee eeeeeee eee eeeeeeeee ee eeee eee eeeeee; eeeee: 8.88 e (88%); ee 88°M/88 Meee; eM88 8.8888.
References
[253] | Meeee, M. M.; Meeeee, M. M., M. Mee. Meee., (8888) 88, 8888. |
[254] | Meeeeeeee, M.; Meeeeee, M.; Meeeeeeeeee, M.; Meeeeeee, M., Meee. Mee. Meee. Me., (8888), 888. |
[255] | Meeeeee, M.; Meeeeeee, M.-M.; Meeeeee, M. M., Mee. Meee., (8888) 8, 888. |
Meeeeee Meeeeeeeeee
- 8.Meeeee-Meee, (8888) 88/8, 888.
- 8.Meeeee-Meee, (8888) M 8e, 88.
- 8.Meeeee-Meee, (8888) M 8e, 88.