Phthalides, rearrangement

Other approaches to alkylidenecycloproparenes have been attempted without success. Aromatization of appropriate alkylidenecyclopropanes or their precursors could not be realized, and flash vacuum pyrolysis of methylene phthalide and 3-methylene-2-coumaranone afforded rearrangement products rather than alkylidenecycloproparenes via extrusion of 002. The photochemical or thermal decomposition of the sodium salt of benzocyclobutenone p-toluenesulfonyl hydrazone led to products derived from dimerization of the intermediate benzocy-clobutenylidene, or from its reaction with the solvent, but no ring-contracted products were observed. When the adduct of methylene-l,6-methano[10]annulene to dicyanoacetylene (249) was subjected to Alder-Rickert cleavage, phenylacety-lene (250) was formed, which derives reasonably from the parent 234. ... 

A second way of synthesizing it is from 2 -carboxy-4-chlorobenzophenone (21.3.21), which during reduction with zinc in acetic acid transforms into 3-(4 -chlorophenyl)phthalide (21.3.27). Sulfonylchlorination of this gives the corresponding snl-fonylchloride (21.3.28), which upon reaction with phosphorous pentachloride is chlorinated into 3-(4 -chlorophenyl-3 -chlorosulfo)-3-chlorophtalide (21.3.25). This is reacted with aqueous ammonia in the aforementioned manner, and it rearranges into chlorothalidone (21.3.26) [50]. 

Cleavage of a C—S bond in the initially formed anion radical has been shown to be the first chemical step in the electrochemically induced rearrangement of 5,5-diarylbenzene-1,2-dicarbothioates to 3,3-bis(arylthio)phthalides in dimethylformamide. The reaction can be effected with 0.1 F/mol and is considered a kind of internal SRN1 reaction (Praefke et al. 1980). 

Solid-state photochemical di-ir-methane-type rearrangement of chiral crystals of 43 have been found to give a mixture of 44 of 44% ee and 45 of 96% ee [25]. When chiral crystals of the thioester 46 were irradiated at 0°C for 6 hr, optically active phthalide 47 of 30% ee was obtained in 65% yield [26],... 

With regard to the mechanism of the solid state photoreactions, there are two possible pathways from the starting amides 53 to phthalides 54 either phenyl migration, which is the same as in the mechanism of thioester derivatives 51, or the mechanism initiated by homolytic cleavage of the C( = 0)-N bond to generate a radical pair intermediate. The radical mechanism has been confirmed in the photo-Fries rearrangement of aromatic amides. To answer the question of the... 

The heating of lactones with powdered alkali cyanides leads to salts of cyano acids. The procedure is illustrated (above equation) by the synthesis of o-carboxybenzyl cyanide from phthalide and potassium cyanide (67-83%). In another instance, the reaction of potassium Cyanide with y-anisyl-y-butyrolactone involves a rearrangement thereby forming a /3-cyano acid instead of the anticipated y-cyano acid, ... 

An interesting Sr 1 reaction occurs on cathodically induced rearrangement of S, S-diphenylbenzene-l,2-dicarbothiolate, forming 3,3-bis(phenylthio) phthalide [79] ... 

The low yield of ortho lithiation, in the above experiments, is presumably due to the formation of the lithio salt of the alcohol in the first instance on treatment with the lithiating agent. Quite often the reaction becomes heterogeneous. A conceivable modification of the above reaction would be lithiation of the corresponding methyl ether derivative. However, in the latter case the reaction takes a different course. The chief reaction now is the formation of the benzylic carbanion which undergoes the Wittig rearrangement When the benzylic position is fully substituted by a carbon residue (such as alkyl or aryl), ortho lithiation occurs in better yield, and further reaction with COj furnishes the 3,3-disubstituted phthalides. 

Irradiation 6f the ester (56) in methanol leads to the rearranged phthalide... 

The reaction is completed within 5-15 min if tetralin at 210 °C is used as solvent. Also, dithio-y-lactones, including dithio-phthalides and dithio-Q -p)Tones, are formed smoothly whereas the hitherto unknown simple or 3-dithiolactones cannot be prepared, neither with LR nor by any other method. Interestingly, dithiopilocarpine is formed as a mixture of diastereomers on reaction of pilocarpine with LR (eq 16), i.e. both oxygen atoms of (12) are replaced by sulfur. In an interesting sequence of thion-ation and rearrangement reactions, three different thiono analogs of 1,8-naphthalic anhydride were prepared (eq 17). ... 

Obtained by Fries rearrange-COCH2CH3 ment of 3,3-bis[4-(propion-yloxy)phenyl]phthalide with aluminium chloride in nitrobenzene at 120-130° for 3 h (20%) [8400]. 

When the phthalides (49) or (50) were heated with concentrated sulphuric acid, rearrangement to (52) took place. " Mixtures of (49), (51), and (52) were... 

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