The iridium (III) complex of pentamethylcyclopentadiene and (S,S) or (R,R)-1,2-diphenyl-N′-tosylethane-1,2-diamine is an effective catalyst for the asymmetric transfer hydrogenation of imines under acidic conditions. However, the enantiomeric excess (ee) of the product amines from the reduction of 1-methyl-3,4-dihydroisoquinolines in either acetonitrile or dichloromethane, decreases exponentially. The dominant cause of the enantioselectivity is the difference in kinetic order of the formation of the two enantiomers with the S-enantiomer being formed in a first-order process whereas that for the R-enantiomer follows zero-order kinetics when (R,R)-TsDPEN is employed, due to different rate-limiting steps for the two processes. A series of 1-fluorinated methyl-3,4-dihydroisoquinolines were synthesised to change the rate-limiting dissociation of the (R) amine product from Ir (III) so that both enantiomers are formed with the same kinetic order. This results in almost complete removal of the enantioselectivity of the reduction. It has been suggested that reduction of imines using transition metal complexes occurs through the neutral imine rather than the more reactive iminium-ion. α-Substituted imines with electron-withdrawing groups make protonation more difficult but enhance the electrophilicity of the imine carbon facilitating nucleophilic attack. The pKa of the iminium ions of 1-fluorinated methyl-3,4-dihydroisoquinolines were determined. Using the relative rates of the cyclopentadienyl iridium (III) complex catalysed reduction of these 1-fluorinated methyl-3,4-dihydroisoquinoline in acetonitrile and, under the acidic conditions of a 5:2 ratio of formic acid:triethylamine, showed that the iminium ion is the reactive species.

The synthesis of chiral molecules is of great importance to the pharmaceutical, agrochemical, flavour and fragrance industries.

The dimeric iodo-iridium complex [IrCp*I 2 ] 2 (Cp*=pentamethylcyclopentadiene) is an efficient catalyst for the racemisation of secondary and tertiary amines at ambient and higher temperatures with a low catalyst loading. The racemisation occurs with pseudo-first-order kinetics and the corresponding four rate constants were obtained by monitoring the time dependence of the concentrations of the (R) and (S) enantiomers starting with either pure (R) or (S) and show a first-order dependence on catalyst concentration. Low temperature 1 H NMR data is consistent with the formation of a 1:1 complex with the amine coordinated to the iridium and with both iodide anions still bound to the metal-ion, but at the higher temperatures used for kinetic studies binding is weak and so no saturation zero-order kinetics are observed. A cross-over experiment with isotopically labelled amines demonstrates the intermediate formation of an imine which can dissociate from the iridium complex. Replacing the iodides in the catalyst by other ligands or having an amide substituent in Cp* results in a much less effective catalysts for the racemisation of amines. The rate constants for a deuterated amine yield a significant primary kinetic isotope effect k H /k D = 3.24 indicating that hydride transfer is involved in the rate-limiting step.

Cyclopropenones in the synthesis of indolizidine, pyrrolo[2,1-a]isoquinoline and indolizino[8,7-b]indole alkaloids

Multilingualism is widespread amongst individuals and communities in African countries. However, language-in-education policies across the continent continue to privilege monolingual approaches to language use in the classroom. In this paper we highlight the colonial origins of these monolingual ideologies and discuss the detrimental effects which arise when learners� linguistic repertoires are not welcomed within the education system. We draw attention to major themes within education across a range of contexts: policy vagueness, teachers as policy implementers, and the creation and imposition of boundaries. We advocate for a language-in-education approach which brings the outside in, which welcomes individuals� lived multilingual realities and which values these as resources for learning. We highlight the ways in which translanguaging could represent a positive shift to the way in which multilingual language practices are talked about, and can contribute to decolonising language policy in African contexts. We conclude by calling to action those working on education and policy to ensure that learners and teachers are better supported. We call ultimately for a rethinking of multilingualism.

The latest language in education policy in Zambia is to use a �familiar� language in the initial stages of education before transitioning into a regional and later foreign language medium. Investigating the use of a familiar language�Namwanga�in Northern Zambia, in the context of a regional language�Bemba�the article shows that learning of literacy in the regional language is better supported by classrooms that allow free use of the �home� language or mother tongue. Results from a reading and comprehension task show no hindrance to the achievement of reading fluency in a regional language when a familiar language is encouraged in the classroom. The article provides support for multi-literacies developed through languages that learners are exposed to in their environment rather than a foreign language.

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The novel dimeric iodo-iridium(III) complex, [Ir(Cp*CONMe2)I2]2, (Cp*CONMe2 = 5-N,N-2,3,4,5-hexamethylcyclopenta-2,4-diene carboxamide) bearing an amide moiety within the tetramethylcyclopentadiene ring, has been synthesised and characterised. The ligand Cp*CONMe2 is synthesised as two...