Cyclopropanones derivatives

In the initial step " the a-halo ketone 1 is deprotonated by the base at the a -carbon to give the carbanion 4, which then undergoes a ring-closure reaction by an intramolecular substitution to give the cyclopropanone derivative 2. The halogen substituent functions as the leaving group ... 

The formation of a cyclopropanone derivative (originally determined by the isolation of degradation products from this unstable species) stimulated considerable interest in this reaction. Tetramethylcyclopropanone, however, cannot be isolated from the reaction mixture under normal photolysis conditions even with the use of an inert solvent. That it is indeed formed as an initial product of a-cleavage results from various trapping experiments in which chemical agents present in the reaction mixture were used to produce stable derivatives of the cyclopropanone [see equation (4.65)]. 

Dimethyl anthracene and diphenyl isobenzofuran form remarkably stable233 cyclopropanone derivatives (353/354), whilst with other diene components (butadiene, tetracyclone, and fulvene) the primarily formed Diels-Alder adducts either suffer ketalizing attack of the solvent (356 - 357, 359 - 358/360) or undergo irreversible changes such as decarbonylation to 362 or rearrangement to 355. 

A possible mechanism for the observed transformation includes the sequence outlined in Scheme 2.327 (i) propargyl (A) - allene (B) tautomerization, (ii) 8jt-cyclization (C), (iii) N-0 cleavage (diradical D), (iv) diradical recombination (cyclopropanone derivative E), and (v) one or two step cyclizations of the azadienyl cyclopropanone into azepinone F. The occurrence of cyclopropanones (type E), as intermediates, is supported by the formation, in some cases, of isoindoles (type I) (789) as minor products (Scheme 2.327) (139, 850, 851). 

Sustituted l-azolin-5-ones have been described thus, 2-ethoxy-1-azolin-5-one (24) is a stable compound that has been prepared from succinimide [80OS(59) 132]. 2-Ethoxy-l-azolin-5-one undergoes a photochemical ring contraction giving cyclopropanone derivatives. The photochemical reaction of (24) in /< r/-butylalcohol as solvent yield tert-butyl A-(l-ethoxy-cyclopropyl)cabamate (25). 

The reaction of carbenes with appropriately substituted olefins provides a useful method for the preparation of many cyclopropanone derivatives. The Simmons-Smith procedure 22> and reactions involving base-generated carbenes, e.g. CHC13/KO-7-Bu, are particularly useful. 

The Simmons-Smith reagent also adds to ketene acetals forming cyclopropanone acetals, as shown in the formation of 1,1-dimethoxy-2,2-dimethylcyclopropane (8) from l,l-dimethoxy-2,2-dimethylethyl-ene.17) Similarly, with methylene iodide, ketene o-xylylene acetal (9) affords the corresponding cyclopropanone derivative (JO) (70%).24)... 

Cyclopropanone acetals may also be prepared by the addition of other one-carbon species to ketene acetals as shown in Table 3. Thus, McElvain and Weyna have synthesized several cyclopropanone deriv-... 

Dibromopropanones may also be reduced electrolytically to form cyclopropanone derivatives as illustrated by the formation 12> of 1-methoxytetramethylcyclopropanol, 38, and l-methoxy-2,2-dimethyl-cyclopropanol, 39, in excellent yields. 

A very plausible mechanism for this would involve loss of hydrogen chloride from XXII to form the bicyclohexanone (XXXII) this is a cyclopropanone derivation and would certainly react at once with alkali to give XXXI. The problem is to explain how this comes about. One possibility might be a-elimination of HC1 from XXX to form a carbene but this seems unlikely such a carbene would in any case be expected to rearrange to cyclohexenone rather than to XXXII. Another possibility would be an internal displacement of chloride ion from the conjugate base of XXX, as indicated in XXXIII this, however, is sterically improbable since in the grouping —CH2—CH=-CO—CHC1— the... 

Scheme 11/21. Synthesis of /3-lactams by ring enlargement of cyclopropanone derivatives, a) CH2C12, -78° b) /-BuOCl, CH3CN c) AgNQ3.

CYCLOPENTANONE ANNULATION VIA CYCLOPROPANONE DERIVATIVES (3a(3.9b)3)-1,2,3a,4,5,9b-HEXAHYDRO-9b-HYDROXY-3a-METHYL-3H-BENZ[ ]INDEN-3-ONE... 

Cyclopentanone Annulation via Cyclopropanone Derivatives cis-3a-Hydroxy-7a-methylbenzinden-l-one. 

TABLE 16. Cyclopropanone derivatives from the addition of a heterosubstituted carbene to an olefin... 

Displacement reactions on 1,1-disubstituted cyclopropanes have been used to prepare other cyclopropanone equivalents. The most readily available 1,1-disubstituted cyclopropanes are geminal dihalo derivatives prepared by the addition of dihalocarbenes to olefins. Unfortunately, these materials do not undergo direct displacement easily and therefore do not provide a general route to other cyclopropanone derivatives. Solvolysis usually leads to ring-opened products, although dibromocyclopropanes with a barrier to... 

PHOTOCHEMICAL RING CONTRACTION OF 2-ETHOXYPYRROLIN-5-ONES TO CYCLOPROPANONE DERIVATIVES tert-BUTYL N-(l-ETHOXYCYCLOPROPYL)CARBAMATE... 

A related example is the proposed intermediacy of the interesting cyclopropanone derivative 8 in the reported transformation of methyl /9-haloethyl dispiro[2.0.2.1]heptan-7-one acetals 7 to tertiary alcohols 9 under the action of alkyllithiumsX Dispiro[2.0.2.1]heptan-7-one (8) reacts more rapidly with tert-butyllithium than 7 when applying only one equivalent of /crt-butyl-lithium, 50% of unreacted 7 was recovered. 

Cyclic enones and dienones undergo a number of photorearrangements. As indicated in Scheme 49, both ring contraction via a [1,2] shift (Zimmerman and Little, 1974) and formation of cyclopropanone derivatives via a... 

Favorski167 noted the formation of acid derivatives when strong bases act on a -halo ketones. The structure of the acid formed can be derived by postulating as intermediate a cyclopropanone derivative whose ring is opened by the base, thus ... 

Lindberg, P., R. Bergman, and B. Wickberg Isolation and structure of coprine, a novel physiologically active cyclopropanone derivative from Coprinus atramentarius and its synthesis via 1-aminocyclopropanol. Chem. Commun. 1975, 946. 

The Favorskii rearrangement is a useful method for the preparation of carboxylic acids or their esters by rearrangement of easily available a-haloketones when the usual methods are not applicable. In the base-promoted reaction, a-haloketones cyclize to cyclopropanone derivatives and then rearrange with ring opening to carboxylic esters (Scheme 8.14). 

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