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Please login to access the full content or check if you have access via Variation 1: Cyclopropanation with Photochemically or Thermally Generated Carbenes

DOI: 10.1055/sos-SD-048-00305

de Meijere, A.; Kozhushkov, S. I.Science of Synthesis, (200948506.

Carbenes are uncharged reactive intermediates that have a divalent carbon atom and consequently react in various ways to complete their valence shells, e.g. by (1) intramolecular rearrangements, (2) intermolecular CH σ-bond insertions, (3) dimerization to alkenes, and (4) cycloadditions to C=C π-bonds. Photolyses or thermolyses of diazomethane, substituted diazomethanes 93, or 3H-diazirines 94 produce highly reactive singlet carbenes 95 that traditionally have been used in cyclopropane synthesis (Scheme 31). However, reactions of such carbenes have a bad reputation because they are difficult to control, as the insertion can occur into primary, secondary, and tertiary CH bonds of an alkane with almost equal ease (see HoubenWeyl, Vol.4/3, pp101, 255 and Vol.E 17a, pp256, 327). Therefore, cyclopropanations with these species can furnish complex mixtures of products with low to moderate yields of the desired cyclopropane derivatives, and preparative GC or HPLC often has to be employed to isolate the product. To increase the yield, the alkene is frequently used as the solvent. Various carbenes generated within cyclodextrins, hemicarcerands, and zeolites demonstrate increased selectivities;[‌142‌] however, this trick has not been widely applied for the synthesis of hydrocarbons with a cyclopropane moiety. Although diazirines 94 have reasonably frequently been used in the synthesis of functionally substituted cyclopropanes,[‌143‌] only a few particular examples for the preparation of pure hydrocarbons, such as the spirocyclopropanated adamantanes, e.g. 9799, from the adamantylidene-substituted diazirine 96, are known.[‌144‌‌146‌]

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Meeeeeeeeee 88

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Me M Me eeee eeeeee, 88°M, 88e 88e [‌888‌]
Me M M eeee eeeeee, 88°M, 88e 88 [‌888‌]

e Meeeeeee ee eeeeeeeeeee MM.

Meeeeeee eeeeeeeee ee eeeeeeeeee ee eeeeeeeeeeee eee eeeeeeeee eeeeeeeeeeeee eee eeee eeee eeeeeeeeee eeee ee eeeeeeeee. Meeeeeee, eeeee ee ee eeeeeeeeeeeee eeeeee eeeeeeeeeeeee ee eeee eeee, eee eeeeee eeeeeeee eeeeeee eeeeeeeeeeeeee eeeeeeeeee eee eeeeeeeeee eeeeee eee eeeeeeeeee eeeeeeeeeeee ee eeeeeeeee eeeeeeeee eeeeeeeeeeeeeee. Meeee eeeeeee eeeeeeeeeeeee eeeeeeeeeeeeeeeee eeee eeeeeeeeeeee ee eeeeeeeeeeeeeeeeeeee,[‌888‌] eeeeeeeeee,[‌888‌] eee 8-eeeeeeeeeeeeeeeee,[‌888‌] ee eeee ee eeeeeeeeeeeeeeeee eeee 8-eeeeeeeeeeeeeeeeeeeee.[‌888‌] Meeeeee, eeeee eeeeeeeeeeee eeeeeee eeeeeee eeeeeeee eeeeeeeeeeee eeeeeeeeee eee eeeeee ee eee eeeeeeee. Meeeeeee, ee eeee eeeee ee ee eee eeeeeee eeeeeee eee eeeeeeeeeeeee eee eee eeeeee ee eeeeeee eeeeeeeeeeeee ee ee eee eeeeeeeeeeeee eeeeeeeeeeeee ee eeeeeeeee eeeeee 8,8-eeeeeee-8M-eeeeeeee (eee Meeeeee[‌888‌] Meeeeee eeeeeeee, eeeeeeeee eeee 8-eeeeeeeeeeeeeee-8,8-eeeee ee eeeeeeeeeeeeee eeeeeeeeeeeeeeeeeeeee 888 ee eeeeeeeeee ee eeeeeeeeeee, eeee eeeee eeeee eeeeeeeeeee ee eeeeeee eeeeeeeee. Meeee eeeeeeee eeeeeee, eeeee eee ee eeeeee ee eee eeeeeeeeee eeeeeee eeeeeee- eee eeeeeeeeeeeeee (eee eeeee), eee eeeee eeee eee eee eeeeeeeeeee ee eeeeeeeeeeeee eeeeeeeeeee eeeeeeeeeeeeeeee 888, eeeeeeee eeeee eeeeeeeeeeeeeeeee eeeee eeeeeee eeee eee ee eeeeeeee eeeeee (Meeeee 88).[‌888‌‌888‌]

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Meeeeeeeeee 88

M8 M8 M8 M8 M8 M8 M8 M8 Meeeeeeeee Meeee (%) Mee
M M M M M M M Me eeee eeeeee, eν, 88°M 88 [‌888‌]
M M M M M M M e-Me eeee eeeeee, eν, 88°M, 8e 88 [‌888‌]
M M M M Me Me Me Me eeee eeeeee, eν, 88°M, 8e 88 [‌888‌]
M M M M Me M Me M Meeeeee 888, eν, 88°M, 8.8e 88 [‌888‌]
M M M M M M eeee eeeeee, eeee 88 [‌888‌]
M M (MM=MM)8 M M eeee eeeeee, eeee 88 [‌888‌]
M M (MM=MM)8 M Me Me M eeeeeee, eν, 88°M, 88e 88 [‌888‌]
M M (MM=MM)8 Me Me M M eeeeeee, eν, 88°M, 88e 88 [‌888‌]
M M (MM=MM)8 M Me M Me eeeeeee, eν, 88°M, 888e 88 [‌888‌]
M M (MM=MM)8 Me Me M M eeee eeeeee, eν, 88°M, 88e 88 [‌888‌]
(MM=MM)8 (MM=MM)8 M M M M Meeeee 88, eν, 888°M e [‌888‌]
(MM=MM)8 (MM=MM)8 Me Me Me Me eeee eeeeee, eν, 88°M, 8.8e 88 [‌888‌]
(MM=MM)8 (MM=MM)8 M M eeee eeeeee, 888°M, 8e 88 [‌888‌]
(MM=MM)8 (MM=MM)8 Me M M M MeMM, eν, 88e 88 [‌888‌]
(MM=MM)8 (MM=MM)8 M M eeeeeee, 88°M, 8.8e 88 [‌888‌]

e Meeee eee eeeeeeee.

Meeeeeeeeeee Meeeeeeee

8,8- eee 8,8-M88-Meeeeeeeeeeeeeeeeeee 88 eee 88:[‌888‌]

M eeee ee eeeeeeeee 88 (88ee, 8.88eeee) eee M88 (88ee, 8.88eeee) ee eeeeeee (88eM) (MMMMMMM: eeeeeeeeee) eee eeeeeeeeee eeee e eeeeee-eeeeeeee Me eeee (eeeeee <888ee) ee e Meeee eeee ee 88°M eee 8e. Meeee eeeeeeeeeeeee ee eee eeee eeeee eeeeeee eeeeeeee, eee eeeeeee eee eeeeeeee ee eeeeeeeeeee MMMM (MMM eeeeee) ee eeee eee eeeeee ee e eeeeeee ee eee eeeeeeeeeeee 88 eee 88 (88:88); eeeee: 88ee (88%). 88 (88ee, 88%) eee 88 (88ee, 88%) eeee eeeeeeeee ee eeeeeeeeeee MMMM eeeee e Meeeeeeee eeeeee. 88: 8MMMM (MM8/eeeeeee-e8, δ): 8.88 (e, 8M), 8.88 (e, 8M, M=88.8Me), 8.88 (e, 8M), 8.88 (e, 8M, M=88.8Me), 8.88 (e, 8M). 88: 8MMMM (MM8/eeeeeee-e8, δ): 8.88 (ee e, 8M), 8.88 (e, 8M), 8.88 (ee, 8M, M=88.8Me), 8.88 (e, 8M), 8.88 (ee e, 8M), 8.88 (e, 8M, M=88.8Me), 8.88 (e, 8M).

eeeee-8,8-Meeeeeeeeeeee[eeeeeeeeeeee-8,8-eeeeee] [888, M8=M8=M8=M8=M; M8,M8=(MM=MM)8; M8=M8=Me]; Meeeeee Meeeeeeee:[‌888‌]

(M)-Mee-8-eee (ee. 88eM) eee eeeeeeeee eeee e eeeeeeeee eeeee-eee (Meeee) Meeeee eeee. M eeee ee eee eeeee eeeeeeee 888 [M8=M8=M; M8,M8=(MM=MM)8; 8.88e, 8.8eeee] ee eeeeeee (8eM) eee eeee eeeee. Mee eeee eee eeeeee eee eeeeee ee 88°M, eee eee eeeeeeee eeee eeeeeeeeee ee eeeeeeee e eeeeeee Me eeee ee 88°M eee 888e eeeee eeeeeeee eeeeeeee. Mee eeee eee eeee eeeeee eee eeeeee, eee eee eeeeee eeeeee eee eeeeeeeeee ee 88°M. Mee eeeeeee eee eeeeeeeee ee e Meeeeeeee eeeeeeeee eee eee eeeeeeeeee eee eeeeeeeee ee eeeeeeeeeee MM ee eeee eee eeeeeee ee e eeeeeeeee eee; eeeee: 888ee (88%); 8MMMM (MMMe8, δ): 8.88 (ee e, 8M, M=8.8Me, MM8), 8.888.88 (e, 8M, eeeeeeeeeee-M), 8.88 (e, 8M, M=8.8Me, MM=), 8.88 (e, 8M, M=8.8Me, MM=), 8.888.88 (e, 8M, eeee-M).