Hydrogen atom donors: recent developments.

This review highlights recent developments in the field of hydrogen atom transfer (HAT) reagents that circumvent the disadvantages of classical group 14 reagents, such as Bu3SnH. Special emphasis is laid on the lowering of bond dissociation energies (BDEs) of molecules that could, as yet, not be used as HAT reagents and on the use of organometallic HAT reagents.

Highly selective Barbier-type propargylations and allenylations catalyzed by titanocene(III).

The alkyne functional group is found in many bioactive natural products and is the key to many important chemical transformations developed over recent years. Moreover, allenes have recently gained relevance as versatile reagents in organic synthesis. Mild, catalytic methods to enable the selective introduction of either alkyne or allene motifs into organic molecules are very valuable but, as yet, quite scarce. We describe an extremely mild and selective method for either the propargylation or allenylation of carbonyl compounds catalyzed by the abundant, safe, and inexpensive metal titanium. These reactions can selectively provide homopropargylic alcohols from aldehydes and ketones or α-hydroxy-allenes from aldehydes. The mechanisms involved were also investigated.

Titanocene(III)-promoted Barbier-type crotylation of carbonyl compounds.

A mild, highly regio- and stereoselective method for the crotylation of aldehydes and ketones mediated/catalyzed by titanocene(III) is described. Optimized conditions permit the selective generation of γ-adducts in high yields together with high stereoselectivity, with a predominance of anti stereoisomers.

Evaluation of a New Workplace Protection Factor-Measuring Method for Filtering Facepiece Respirator.

BACKGROUND: This study aims to assess whether the TSI PortaCount (Model 8020) is a measuring instrument comparable with the flame photometer. This would provide an indication for the suitability of the PortaCount for determining the workplace protection factor for particulate filtering facepiece respirators. METHODS: The PortaCount (with and without the N95-Companion™) was compared with a stationary flame photometer from Moores (Wallisdown) Ltd (Type 1100), which is a measuring instrument used in the procedure for determining the total inward leakage of the particulate filtering facepiece respirator in the European Standard. Penetration levels of sodium chloride aerosol through sample respirators of two brands (A and B) were determined by the two measuring systems under laboratory conditions. For each brand, thirty-six measurements were conducted. The samples were split into groups according to their protection level, conditioning before testing, and aerosol concentration. The relationship between the gauged data from two measuring systems was determined. In addition, the particle size distribution inside the respirator and outside the respirator was documented. Linear regression analysis was used to calculate the association between the PortaCount (with and without the N95-Companion™) and the flame photometer. RESULTS: A linear relationship was found between the raw data scaled with the PortaCount (without N95-Companion™) and the data detected by the flame photometer (R2 = 0.9704) under all test conditions. The distribution of particle size was found to be the same inside and outside the respirator in almost all cases. CONCLUSION: Based on the obtained data, the PortaCount may be applicable for the determination of workplace protection factor.