Combined experimental and computational investigations of rhodium-catalysed C-H functionalisation of pyrazoles with alkenes

Detailed experimental and computational studies have been carried out on the oxidative coupling of the alkenes C(2)H(3)Y (Y=CO(2)Me (a), Ph (b), C(O)Me (c)) with 3-aryl-5-R-pyrazoles (R=Me (1 a), Ph (1 b), CF(3) (1 c)) using a [Rh(MeCN)(3)Cp*][PF(6)](2)/Cu(OAc)(2)⋅H(2)O catalyst system. In the reaction of methyl acrylate with 1 a, up to five products (2 aa–6 aa) were formed, including the trans monovinyl product, either complexed within a novel Cu(I) dimer (2 aa) or as the free species (3 aa), and a divinyl species (6 aa); both 3 aa and 6 aa underwent cyclisation by an aza-Michael reaction to give fused heterocycles 4 aa and 5 aa, respectively. With styrene, only trans mono- and divinylation products were observed, whereas with methyl vinyl ketone, a stronger Michael acceptor, only cyclised oxidative coupling products were formed. Density functional theory calculations were performed to characterise the different migratory insertion and β-H transfer steps implicated in the reactions of 1 a with methyl acrylate and styrene. The calculations showed a clear kinetic preference for 2,1-insertion and the formation of trans vinyl products, consistent with the experimental results

Ambiphilic C-H activation routes to heterocycles

This thesis describes investigations of Cp*Rh- and (p-Cy)Ru-catalysed C-H functionalisation reactions of various substrates with alkynes and alkenes for the formation of several heterocycles and carbocycles. Mechanistic studies and DFT calculations are also presented. Chapter One includes a discussion of different mechanisms of C-H activation namely oxidative addition, σ-bond metathesis, 1,2-addition, electrophilic activation and AMLA/CMD. The applications of these different mechanisms of C-H activation in catalysis are also discussed with a particular emphasis on the use of AMLA/CMD in direct arylation reactions. Chapter Two gives an overview of stoichiometric and catalytic studies of AMLA C-H activation and subsequent reactivity with alkynes at Ir, Rh, and Ru. The results of Cp*Rh- and some (p-Cy)Ru-catalysed reactions of C-phenylpyrazoles with alkynes are presented. N-H and C-H activation occurs, leading to heterocycles. Mechanistic studies and DFT calculations show that C-H activation is reversible and rate limiting in the cases examined. Chapter Three is similar to Chapter Two but focusses on reactions with alkenes. The Cp*Rh-catalysed reactions of C-phenylpyrazoles with alkenes lead to mono or divinyl products which may undergo further aza-Michael cyclisations if the alkene is a good Michael acceptor. Mechanistic studies and DFT calculations are also discussed. Chapter Four deals with Cp*Rh-catalysed coupling reactions of other directing groups, including imidazole, imidazoline, pyrazolidinone, hydrazine, carboxylic acid and oxime with alkynes. Again, there is discussion on the different factors affecting product selectivity. Chapter Five gives a summary of all the conclusions on the work presented in this thesis. Throughout the thesis, all new compounds are characterised spectroscopically and several compounds have been characterised by X-ray crystallography

The Institutionalization of Family Welfare : The Social Division of Labour in the Field of Child Care in Austria and Germany

Comparative research on family policies has primarily focused on governmental activities for the family. Public expenditures and single governmental measures have been at the core of current discussion, with a specific focus on their impact on particular social situations of families as well as on particular family forms. Thus, most of the debate is state-centred, neglecting the role of collective actors in civil society, such as the Church, in providing family welfare. The aim of this paper is to study the division of labour between family, government and civil society on the one hand and its consequence for the division of labour within the family on the other hand in the field of child care. After presenting a short overview of the present state of comparative research, I will develop a theoretical framework for studying the social division of labour in the field of family welfare. Following this theoretical approach, I will describe the social division of labour in the field of child care. In order to develop an institutional map of child care in Europe, I will compare Austria and Germany as exemplary cases. There are huge variations in these patterns to be found all across Western European societies. Thus, in the part to follow, I try to explain these similarities and differences with reference to the origins and development of the division of labour in the field of child care. For this purpose, I choose an historical and interpretive approach following Stein Rokkan. Thus, I will study and compare the country-specific configurations of cleavages from their origins, the social actors organizing along these lines of conflicts, and their ideas for problem-solving in the field of child care

Combined Experimental and Computational Investigations of Rhodium- and Ruthenium-Catalyzed C–H Functionalization of Pyrazoles with Alkynes

Detailed experimental and computational studies are reported on the mechanism of the coupling of alkynes with 3-arylpyrazoles at [Rh­(MeCN)₃Cp*]­[PF₆]₂ and [RuCl₂(<i>p</i>-cymene)]₂ catalysts. Density functional theory (DFT) calculations indicate a mechanism involving sequential N–H and C–H bond activation, HOAc/alkyne exchange, migratory insertion, and C–N reductive coupling. For rhodium, C–H bond activation is a two-step process comprising κ²–κ¹ displacement of acetate to give an agostic intermediate which then undergoes C–H bond cleavage via proton transfer to acetate. For the reaction of 3-phenyl-5-methylpyrazole with 4-octyne <i>k</i>_H/<i>k</i>_D = 2.7 ± 0.5 indicating that C–H bond cleavage is rate limiting in this case. However, H/D exchange studies, both with and without added alkyne, suggest that the migratory insertion transition state is close in energy to that for C–H bond cleavage. In order to model this result correctly, the DFT calculations must employ the full experimental system and include a treatment of dispersion effects. A significantly higher overall barrier to catalysis is computed at {Ru­(<i>p</i>-cymene)} for which the rate-limiting process remains C–H activation. However, this is now a one-step process corresponding to the κ²–κ¹ displacement of acetate and so is still consistent with the lack of a significant experimental isotope effect (<i>k</i>_<i>H</i><i>/k</i>_<i>D</i> = 1.1 ± 0.2)