A-Cyclopropyl ketones

For a convenient photochemical preparation of steroidal a-cyclopropyl ketones from the A -pyrazoline derivatives of the corresponding a, -unsaturated ketones, cf. ref. 50. 

Photochemical cyclohex-2-enone bicyclo (3.1.0)hexan-2-one rearrangement, 320 Photochemical a-cyclopropyl ketone isomerization, 313... 

Cyclopropyl-2-hydroxyalkyl sulphoxides 416 can be obtained either by addition of an a-sulphinyl carbanion to a cyclopropyl ketone, or from alkyl 3-chloropropyl ketones and two moles of an a-sulphinyl carbanion493 (equation 247). 

Another interesting cationic domino process is the acid-induced ring opening of a-cyclopropyl ketones and subsequent endocyclic trapping of the formed carboca-... 

Chlorohydrins. F.poxides can be cleaved to frotw-chlorohydrins with pyridinium hydrochloride in chloroform or pyridine. The reagent also cleaves a-cyclopropyl ketones to mixtures of y-chloro ketones obtained by the two possible modes of cyclo-propyl ring fission.2... 

Treatment of a-cyclopropyl ketones with lithium in a mixture of N,N-d2-propylamine and hexamethylphosphortriamide is a recently reported method for deuterium labeling via reductive ring opening.85 This reaction provides y-labeled ketones in good yield (70-100%) and isotopic purity (85-93%). 

The TiCU-induced three-component coupling reaction of an a-haloacylsilane, allylsilane and another carbonyl compound gives 48 in good yield. A silyl enol ether intermediate is suggested (equation 31)82. The reaction of a cyclopropyl ketone with allylsilane yields a mixture of skeletal rearranged products83. 

Tenney, L.P., Boykin, D.W. Jr, and Lutz, R.E. (1966) Novel photocydization of a highly phenylated p.y-uri saturated ketone to a cyclopropyl ketone, involving benzoyl group migration. Journal of the American Chemical Society, 88 (8), 1835-1836. 

Radical Anionic Photocyclization of the a-Cyclopropyl Ketone (79) [300 20nm Photolysis on a 0.9 mmol Scale] [48b]... 

Oxa-di-TT-methane rearrangement A photochemical reaction of a P,y-unsaturated ketone to form a saturated a-cyclopropyl ketone. The rearrangement formally amounts to a 1,2-acyl shift and bond formation between the former a and y carbon atoms. 

Cleavage of a cyclopropyl ketone. Reaction of 1 with benzeneselenenyl chloride at room temperature gives a mixture of 2 and 3. The latter compound was converted into ( )-erysotramidine (4) by reaction with CHjOH and AgNOs followed by desulfurization with Raney nickel (507o overall yield). 

Diazomethane adds across the C=C bonds of suitable conjugated ketones to give pyrazolines [28g], Initial attack of the nucleophilic reagent upon the jS -carbon gives an intermediate 36) which cyclises to form a five-membered ring, in preference to a cyclopropyl ketone (with loss of Ng), presumably because of the greater strain which would be introduced in the latter system. 

This reagent is used as a Lewis acid catalyst for the intramolecular addition of diazo ketones to alkenes [130], The direct synthesis of bicyclo[3.2.1]octenones from the appropriate diazoketones using BF3 Et20 (Eq. 76) is superior to the copper-catalyzed thermal decomposition of the diazo ketone to a cyclopropyl ketone and subsequent acid-catalyzed cleavage [131]. 

A Cyclopropyl Ketone from a Polychlorinated Acetal A True Challenge... 

For the ring expansion step an extra carbon is needed, of course, and the 7 carbon of the lactone ring appears to be the best candidate. It not only bears a relatively labile C-O bond that upon disconnection might evolve into the carboxylate unit required for decarboxylation, but this carbon is also proximal to the a anion of the cyclohexanone portion of molecule I that is expected to appear in strong basic medium. The union of these two carbons will produce a cyclopropyl ketone whose central C-C bond might break up, prodded by the carbonyl unit, to yield a seven-membered ring system. 

In Table 11 UV absorption and CD data of a series of aliphatic trans-substituted a-cyclopropyl ketones II are summarized. Though the absorption intensity (e) varies by a... 

TABLE 11. (n, n ) and (n n ) absorption and CD characteristics of aliphatic trans-substituted a-cyclopropyl ketones (ii)io9.no... 

Additional applications of this intriguing method to create polyquinanes include synthesis of hirsutene, modhephen, and silphinene employing acid-induced or reductive cleavage of a vinylcyclopropane and opening of a cyclopropyl ketone with a... 

Another successful alkylation of a cyclopropyl ketone was reported by Handel and CO workers when they reacted cyclopropyl phenyl ketone (211) with excess potassium hydride (5 M equivalents) in the presence of [2.2.2]cryptand methylation with methyl iodide gave 212 in 90% yield. The conditions are crucial without the cryptand, 211 is reduced to the corresponding secondary alcohol in 82 % yield. 

During a synthesis of taxoF the reductive cleavage of a cyclopropyl ketone with Sm/HMPA-MeOH gave rise to an enol which was processed further. 

Substituted a-cyclopropyl ketones 4 result from the reaction of various 2-oxoalkylphos-phonate carbanions with simple and functionalized oxiranes in 40-70% yield. ... 

In some cases, the reaction between an amine and a cyclopropyl ketone stops before elimination of water takes place, thus giving a 1-alkylamino-l-hydroxyalkylcyclopropane as the product (see Section 5.2.5.1.8.2.10.). 

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