Cyclopropyl aldehydes

In order to determine whether the partial suppression of the free-rotor effect was required for the success of the ODPM rearrangement process, the study was extended to the aldehyde 33 [51], When 33 is irradiated (15 min), under similar conditions to those used for 29, the cyclopropyl aldehyde 34, resulting from an ODPM rearrangement, was obtained, as the tran -diastereoisomer, in 90% isolated yield. This result demonstrated clearly that the ODPM reactivity of (3,y-unsaturated aldehydes is not restricted to cyclic compounds, such as 29, but can also be extended to acyclic derivatives. Therefore, the suppression of the free-rotor effect is not essential for the success of the rearrangement and the reaction is probably controlled by both the excitation of the molecule to the TiCtt, -it )... 

To confirm this hypothesis the photoreactivity of aldehyde 23, previously reported as unreactive in the ODPM mode [47], was reinvestigated. The results obtained show that wi-methoxyacetophenone-sensitized irradiation of 23 (2 hr) brings about the formation of the cyclopropyl aldehyde 11, resulting from an ODPM rearrangement, in 57% isolated yield. Further support for the above postulates was obtained from studies of triplet-sensitized irradiation of aldehydes 22, 35, and 36. These substances undergo the ODPM rearrangement to yield the corresponding cyclopropyl aldehydes 37 (82%), 38 (83%) and 39 (96%), respectively [51]. 

The possible competition between ODPM and DPM processes was also studied. Triplet-sensitized irradiation of 44 for 10 min affords the cyclopropyl aldehyde 45 (19%) resulting from an ODPM rearrangement, exclusively. However, under the same conditions, aldehyde 46 yields the cyclopropyl aldehyde 47 (48%), resulting from a DPM rearrangement [51]. 

A branched-chain iodo sugar derivative, l,5-anhydro-4,6-0-benzyl-idene-2,3-dideoxy-3-C-(iodomethyl)-D-rifoo-hex-l-enitol [4,6-O-ben-zylidene-3-deoxy-3-C-(iodomethyl)-D-allal] (200), is one of the products formed on treatment of methyl 4,6-0-benzylidene-2,3-dideoxy-a-D-en/thro-hex-2-enopyranoside (77) with the Simmons-Smith reagent (diiodomethane and zinc-copper couple).123,212 Compound 200 displays high solvolytic reactivity, an observation that has been rationalized by supposing the formation of the highly stabilized carbonium ion213 (201). Thus, under conditions wherein methyl 2,3,4-tri-0-acetyl-6-deoxy-6-iodo-a-D-glucopyranoside required more than 24 hours to react appreciably with an excess of silver nitrate in 50% aqueous p-dioxane buffered with silver carbonate, the iodide 200 was hydrolyzed completely in less than 1 minute the product of hydrolysis of 200 is the cyclopropyl aldehyde 202. Methanolysis of... 

Cyclopropyl aldehydes.2 The reagent is a more reactive 1,3-dipole than alkyl dia/oacctatcs. It reacts with various olelins such as styrene, methyl acrylate, and 2 to form pyrazolincs a, which on photolysis arc converted into the cyclopropyl acelals b. The free aldehydes (3) are obtained by acid hydrolysis in overall yields greater than 80%. 

Cyclopropanols and their derivatives Diiodomethane-Samarium, 113 Trimethylstannylmethyllithium, 331 Cyclopropyl aldehydes, ketones, esters, etc. 

Disilenes react with ketones, aldehydes, esters and acid chlorides by formal [2 + 21-cycloaddition to yield the corresponding disiloxetanes (equation 73)8,16. The reaction is non-concerted and proceeds through the initial formation of a 1,4-biradical intermediate, as has been shown by the products of reaction of tetramesityldisilene (110) with the cyclopropyl aldehyde 117 (equation 90)163. The absolute rate constants listed in Table 19 indicate there to be a significant difference in reactivity between the monophenyl-substituted disilene 103 and the 1,2-diphenyl-substituted derivatives 104, consistent with a steric effect on the rate of formation of the biradical intermediate. As would be expected, no kinetic deuterium isotope effect is discernible from the relative rates of addition of acetone and acetone- to these compounds. 

Reaction with cyclopropyl alcohols and ketones. The primary and secondary cyclopropyl alcohols 1 and 2 are converted by reaction with P2I4 or PI, mainly into the corresponding iodides. In contrast, the tertiary a-cyclopropyl alcohol 3 is converted into the homoallylic iodide 4 under very mild conditions. a-Cyclopropyl aldehydes and ketones are also cleaved by P2I4 to -y-iodo carbonyl compounds in high yield, particularly when the solvent is acetone. 

Platinum(ll)-catalyzed carbocyclization of a.ty-enynes has been intensively researched lately. For instance, 2-disubstituted l-en-6-ynes react with methanol in the presence of PtCl2 as catalyst to form carbocycles with exocyclic aUcenes. The analogous reactions of 3-allyl propargyl ether or 3-allyl propargyl tosylamine in water using the same catalysts will generate cyclopropyl aldehydes besides the product of cycloisomerization (Scheme 82). The coordination of the... 

This reaction has been developed by Stevens for a refined access to various alkaloid families. Equation 29 shows the short synthesis of mesembrine, where methyl vinyl ketone is annulated to the endocyclic enamine. The precursors for the imines are usually cyclopropyl aldehydes and the corresponding amines or cyclopropyl nitriles combined with suitable organometallics as demonstrated in a simple myosmine synthesis (equation 30). Additional examples will not be discussed here since excellent review articles exist on this topic ... 

It has been proposed that the decarbonylation of aldehydes by the Wilkinson catalyst [RhCl(PPh3)3] involves a radical pair disproportionation or recombination reaction. A radical pair intermediate in solution is equivalent to a cage reaction (Scheme 6). Table 15 shows the results obtained from the decarbonylation of a series of chiral cyclopropyl aldehydes ... 

In an application of (Z)-selective alkene formation to enolizable aldehydes, it was noted that the combination of LiCl and DBU was effective for deprotonation by lithium complexation of the Still phosphonate. In this example, the cyclopropyl aldehyde (176) reacted chemoselectively in the presence of the ketone (equation 43). In addition, the ( )-alkene could be synthesized by lithium coordination with a standard HWE methyl phosphonate. As this example illustrates, the trifluoroethyl phosphonate can fill an important void by providing trisubstituted alkenes with sensitive substrates in go< selectivity. From the examples of Marshall and Oppolzer it appears that the application of the reaction to higher order trisubstituted alkenes is selective for the (Z)-isomer. The magnitude of the selectivity is substrate specific and dependent on the rapid rate of eo firo-a-oxyphosphonate decomposition. 

Cyclopropyl aldehydes, 120-121 Cyclopropyl ketones, 218 Cyclopropyl phenyl ketone, 112 Cyclopropyl phenyl sulfides, 231 Cyclosativene, 24... 

Epoxycyclobutanes 5 afforded cyclopropyl aldehydes and ketones 6 in good to excellent yields when treated with sulfuric acid or hydrogen chloride. The use of aluminum trichloride as the acidic reagent generally leads to mixtures of cyclopropylcarbonyl compounds and cyclobutanones. 

In a similar manner trans- and c/x-cyclobutane-l,2-diols afforded cyclopropyl aldehydes and ketones 7 and 8 on treatment with 4-toluenesulfonic acid in benzene or boron trifluoride-diethyl... 

Irradiative (185 nm) conversion of the dihydrofurans (198) affords the cyclopropyl aldehydes (199). ... 

Oxa-di-Jt-methane rearrangement leads to cyclopropane derivatives, compounds that are otherwise difficult to synthesize. The diphenylenal 88, for example, is converted to the cyclopropyl aldehyde 89 by triplet sensitization (Scheme 6.35).660 The photoproduct can be further transformed to other compounds, for example a diphenylvinylcyclopropane derivative 90. 

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