Stability, reactivity, solution, and solid-state structure of halomethylzinc alkoxides.

In this paper, we report our findings regarding the development of a Lewis acid-catalyzed cyclopropanation of allylic alcohols with bis(iodomethyl)zinc. Iodomethylzinc alkoxides can be formed by treatment of an alcohol with bis(iodomethyl)zinc. These species are not prone to undergo cyclopropanation at low temperature but the addition of a Lewis acid in catalytic amounts induces the cyclopropanation reaction. Using this procedure, we demonstrated that the Lewis acid-catalyzed pathway significantly overwhelms the uncatalyzed one. This paper describes fundamental issues regarding the preparation and stability of halomethyl zinc alkoxides in solution as well as their aggregation state in solution and solid-state structures. Furthermore, the competition reaction between the inter- vs intramolecular cyclopropanation will be studied. Finally, we will discuss the possible activation pathways to explain the Lewis acid activation of halomethylzinc alkoxides. These findings provided new insights on the reactivity of ROZnCH(2)I and established the groundwork for the elaboration of an enantioselective version of the reaction.

Catalytic asymmetric cyclopropanation of allylic alcohols with titanium-TADDOLate: scope of the cyclopropanation reaction.

A substoichiometric amount of titanium-TADDOLate complex was effective at catalyzing the cyclopropanation reaction of allylic alcohols in the presence 1 equiv of bis(iodomethyl)zinc. After initial optimization of the catalyst structure, excellent yields and enantiomeric ratios were obtained for 3-aryl- or 3-heteroaryl-substituted allylic alcohols (up to 97:3). Alkyl-substituted allylic alcohols gave modest yields and enantiomeric ratios (up to 87:13) but these compare favorably with those observed with other substoichiometric chiral ligands. The full synthetic scope of the reaction is presented in this paper.

Enantioselective synthesis of spiropentanes from hydroxymethylallenes.

[reaction: see text]. Hydroxymethylallenes are efficiently converted to the corresponding spiropentanes in high yields and enantiomeric ratios upon treatment with Zn(CH2I)2 and dioxaborolane ligand 1. The reaction also proceeds with complete diastereocontrol. The application of this methodology to the synthesis of spiropentaneacetic acid is also presented.

Optical remote sensing inside an inhomogeneous axisymmetric medium: the absorption field measurement.

It is shown that the absorption field inside an inhomogeneous, rotationally symmetric medium with a spatially variable refractive index can be reconstructed by means of a tomographic technique. The classic Abel transform is extended to non-Euclidean optical media. The optical behavior of such a medium is described and, provided that the product of the refractive index with the radial distance is a monotonic function, an exact inverse formula is found. Both a numerical and an analytical test on a phantom function is carried out to prove the exactness of this formula. In contrast, when the assumption of a monotonic function is not true, it is shown that the reconstruction problem becomes subdeterminate because of the presence of annular regions, known as blind areas, inside of which no curved path reaches an extremum. The spatial localization and the size of these regions are related to the extrema of the index of refraction times the radial distance.

Bridging the gap between hemodynamics and monitoring.

Hurst states that "hemodynamic monitoring is a complement of, rather than a replacement for, clinical judgment." Holder explains that "hemodynamic parameters add sufficient clarity for physicians to a difficult patient management problem." However, it is nursing which must bring clarity to the parameters. It is the nurse who must be ever-vigilant and strive for excellence in invasive hemodynamic monitoring of critically ill patients--as the caregiver who is with the patient 24 hours a day, 7 days a week. Effective hemodynamic monitoring starts with an understanding of the hemodynamic mechanisms that monitoring aims to measure. Then, measuring the hemodynamic mechanisms requires technical expertise to provide accurate parameters from the monitoring equipment. Lastly, an appreciation for the risks and benefits, together with patient responses to being monitored, helps the nurse evaluate the contribution invasive hemodynamic monitoring has on patient outcomes. Nurses who couple knowledge of cardiovascular physiology, technical expertise, and thorough assessment and diagnosis of patient responses to hemodynamic instability and invasive monitoring bring the essence of holistic nursing care to hemodynamic monitoring.

The use of physician services under a national health insurance scheme. An examination of the Canada Health Survey.

In this paper the individual is employed as the unit of analysis to examine the extent to which the use of physician care by beneficiaries insured under the Canadian Medicare program is determined by medical needs and sociodemographic characteristics as opposed to economic considerations. The data were derived from the Canada Health Survey, which is a stratified, multistaged sample of the entire population. The results of the discriminant and weighted multiple regression analysis indicate that the use or nonuse of service and the volume of physician care consumed is determined by medical needs and sociodemographic characteristics rather than by economic status. Accordingly, the findings of this study are consistent with the contention that the Medicare program has resulted in an equitable distribution of physician service.