Unusually weak metal-hydrogen bonds in HV(CO)4(P-P) and their effectiveness as H(*) donors.

The V-H bonds in HV(CO)4(P-P) are unusually weak (55 to 58 kcal/mol). They transfer H* to styrene more rapidly than CpCr(CO)3H does and are effective stoichiometric reagents for the cyclization of appropriate 1,6-dienes.

Nucleophilic additions of trimethylsilyl cyanide to cyclic oxocarbenium ions: evidence for the loss of stereoselectivity at the limits of diffusion control.

The limitations of stereoelectronic models in assessing the stereoselective nucleophilic substitution reactions of cyclic oxocarbenium ions at high reaction rates are discussed. Evidence is provided suggesting that the diastereoselectivity of nucleophilic substitution reactions is attenuated at the limits of diffusion control. The low diastereoselectivities observed in the reactions of trimethylsilyl cyanide with five- and six-membered ring oxocarbenium ions are attributed to the high reactivity of the nucleophile and its reactions with these electrophiles at diffusion control rates.

Electrostatic interactions in cations and their importance in biology and chemistry.

Electrostatic effects exert strongly stabilizing influences on cations, in many cases controlling the conformational preferences of these cations. The lowest energy conformers are ones where the positive charge is brought closest to substituents bearing partial negative charges. These conformational biases, along with stereoelectronic effects, can control the stereoselectivity of reactions involving carbocationic intermediates.

Barriers facing junior doctors in rural practice.

INTRODUCTION: Early postgraduate, or junior doctors, are still required to practise in rural and remote communities, and they continue to face numerous issues and difficulties. Within the hospital setting, exposure to rural practice appears to be very limited during internship, and also to some extent, during the second postgraduate year and beyond. This is a major issue for those required to undertake country relieving, rural terms or who will be bonded to rural and remote practice for several years after internship. This research investigated the current issues and difficulties faced by junior doctors, required to undertake rural and remote practice in Queensland, Australia. METHODS: An exploratory study was undertaken. Primary data were collected through semi-structured interviews held with key stakeholders. Stakeholders included: directors of clinical training; medical educators; junior doctors; rural practitioners; academic rural practitioners; and medical administrators. Of the 23 people approached, a total of 19 agreed to be interviewed. The response rate was 82.6%. RESULTS: Similar to the issues identified in the literature, there are currently a number of barriers influencing the ability of junior doctors to practise competently and confidently when undertaking practice in rural and remote communities. Minimal clinical experience, lack of supervision and on-site support, inadequate orientation and uninformed expectations, limited access to relevant education, and the influence of isolation, results in an overall lack of preparation both professionally and personally. When asked, respondents supported the identification of core skills and knowledge, and integration of these and other issues affecting rural practice, into their hospital-based programs. Current hospital-based education and training programs were not adequately preparing junior doctors for rural and remote practice. It was commented that orientation and education, with a rural emphasis, could assist junior doctors in their preparation for country relieving, rural terms and longer placements. CONCLUSIONS: Data collected in this study have confirmed that junior doctors are still being sent to undertake country relieving in their second postgraduate year. Hence, the issues remain for junior doctors when undertaking practice in rural or remote communities, including country relievers and scholarship holders. Results from this study suggest that prior recommendations have not been fully implemented. A recommendation is that initiatives at the undergraduate level, including increasing rural exposure and integration of rural context into training, be further developed at the early postgraduate level. Core rural competencies should be identified and realistic preparation and support strategies put in place in the hospital setting. This will further the effort to prepare junior doctors for rural practice and minimise some of the barriers currently experienced.

Stereoselective C-glycosylation reactions of ribose derivatives: electronic effects of five-membered ring oxocarbenium ions.

The factors controlling the highly alpha-selective C-glycosylation of ribose derivatives were determined by examining the stereoselective reactions of 18 ribose analogues differing in substitution at C-2, C-3, and C-4. The lowest energy conformers of the intermediate oxocarbenium ions display the C-3 alkoxy group in a pseudoaxial orientation to maximize electrostatic effects. To a lesser extent, the C-2 substituent prefers a pseudoequatorial position, and the alkyl group at C-4 has little influence on conformational preferences. In all cases, the product was formed by stereoelectronically preferred inside attack on the lowest energy conformer.

Using stereoelectronic effects to explain selective reactions of 4-substituted five-membered ring oxocarbenium ions.

[reaction: see text] The utility of the inside attack model to predict and analyze the stereoselectivities of nucleophilic additions to complex five-membered ring oxocarbenium ions is demonstrated in a systematic study of C-4-substituted acetals.

Nucleophilic additions to fused bicyclic five-membered ring oxocarbenium ions: evidence for preferential attack on the inside face.

Evidence is provided that nucleophilic attack on five-membered ring oxocarbenium ions occurs from the inside face of the envelope. An eight-five fused-bicyclic system in which two substituents are constrained to pseudoequatorial positions underwent nucleophilic addition with selectivity that was comparable to an unconstrained monocyclic system. On the other hand, a bicyclic six-five analogue underwent reaction with low selectivity. This observation indicates that minimization of eclipsing interactions by attacking inside the envelope is not enough to control selectivity, but that the changes in the overall three-dimensional structure of the ring must be favorable as well. In the bicyclic six-five series, the six-membered ring is accommodated in the cation, but it destabilizes the transition state structure leading to the first-formed product of inside attack.