Carmen Z. Smith

Modification of pathways for cathodic reduction via complexation with β-cyclodextrin

Complexation of electroactive substrates with β-cyclodextrin can profoundly alter the course of their reactions; for the cathodic reduction of complexes of ethyl cinnamate, benzaldehyde, and benzophenone protonation of radical-anions is highly efficient whereas a previously unobserved reductive coupling is found for the acetophenone complex.

The X-ray crystal structure of an ethyl cinnamate–β-cyclodextrin guest–host complex

An X-ray crystallographic determination of the structure of the title complex reveals that the ester function protrudes from the torus at the side bearing primary hydroxy-groups; this strengthens recent rationalisations of the electro-organic reactions of such complexes.

Electro-organic reactions. Part 52: Diels–Alder reactions in aqueous solution via electrogenerated quinodimethanes

ortho-Quinodimethanes (o-QDMs) are conveniently generated cathodically in aqueous electrolyte in the presence of N-methylmaleimide, which acts as both redox mediator and dienophile. endo-Diels–Alder adducts are formed efficiently and rapidly and competition from electrohydrodimerisation of N-methylmaleimide is completely suppressed. Kinetic and coulometric evidence suggests that initial electron transfer is to a complex between the o-QDM precursor and N-methylmaleimide (hydrophobic packing).

Redox enzyme models. Catalysis of the cathodic cleavage of benzyl esters via complexation with a substituted β-cyclodextrin

β-Cyclodextrin substituted at the 6-position with an electrophore (o-benzoylbenzoate) complexes with modest reduction potential of the electrophore.

Electro-organic reactions. Part 51. Reactivity and stereochemical pathways for cathodically generated radical-anions of α,β-unsaturated ketones in aqueous media

The cathodic reduction of α,β-unsaturated ketones in aqueous electrolyte gives efficient C–C coupling with the high stereoselectivity associated with similar reactions in aprotic media. The key features of these reactions are consistent with those expected from the likely mechanism involving water-templated coupling of radical-anions. As a further consequence the stereochemistry of the major products (cyclopentanols and linear hydrodimers) has been unambiguously assigned using X-ray crystallography and 2D NOESY 1H NMR experiments.

Synthesis of [19-2H3]progesterone and [18-2H3]progesterone

[19-2H3]Progesterone has been prepared from 3,3 : 20,20-bisethylenedioxy[19-2H3]pregn-5-en-19-ol by reduction of the derived 19-toluene-p-sulphonate with lithium triethylborodeuteride (‘superdeuteride’) followed by hydrolysis of the ethylenedioxy groups. [18-2H3] Progesterone was obtained from (20R)-3β-acetoxy-pregn-5-eno-20,18-lactone via conversion into methyl (20R)-3β-20-dihydroxypregn-5-en-18-oate: a two-stage introduction of three atoms of deuterium at C-18 via the toluene-p-sulphonate of the derived [18-2H2]-18-ol required unusual experimental conditions.

Remote anodic oxidation of carboxylic acids in fluorosulphuric acid: a synthesis of lactones and unsaturated cyclic ketones

The oxidation of octanoic, heptanoic, 4-methylpentanoic, and 5-methylhexanoic acids at a smooth platinum anode in fluorosulphuric acid containing potassium fluorosulphate (1M) at 273 K is described. Oxidation leads to cleavage of a C–H bond and formation of a cationic centre at a place in the carbon skeleton remote from the functional group. The final products isolated are 5- and 6-membered ring compounds, lactones, and unsaturated cyclic ketones, and the ratio of products depends on the length of time the anolyte solution is left prior to work-up. A mechanism which explains the formation of all products is suggested.

Remote oxidation of carboxylic acids by peroxodisulphuryl difluoride in fluorosulphuric acid: a general synthesis of lactones

Peroxodisulphuryl difluoride, (FSO3)2, generated by constant-current electrolysis of fluorosulphuric acid–potassium fluorosulphate (1.0M), reacts rapidly and smoothly with a series of carboxylic acids (C3–C10) in fluorosulphuric acid at 273 K. Oxidation occurs at a site remote from the carboxy-group and, after work-up, lactones can be isolated in high yields.

Clarification of the ring-closure of certain 4,5-diaminopyrimidines to 6-substituted 8-alkylpurines

Acylation of 5,6-diaminopyrimidin-4(3H)-one (I) furnished the bisacylamino-derivatives (IIa–d). Contrary to previous reports, treatment of these diamides (IIa–d) with refluxing aqueous base did not furnish 8-alkylpurines, but the monoacylaminopyrimidinone derivatives (IIIa–d). The monoacylamino-derivatives (IIIa–d) are conveniently ring-closed to 8-alkyl-6-chloro-9H-purines with phosphoryl chloride. Acylation of 4,5,6-triamino-pyrimidine (VI) gave monoacylamino-derivatives (VIIa and b) which underwent ready ring-closure to 8-alkyl-9H-adenines (VIIIa and b) in aqueous alkali.