On the roles of protic solvents in imidazolidinone-catalyzed transformations

The effect of protic solvents on the rate and stereochemical outcome of the imidazolidinone-catalyzed Diels–Alder cycloaddition was rationalized. The following picture emerges: the solvent accelerates iminium ion formation (step 1), the Diels–Alder cycloaddition is reversible (step 2), and the solvent intercepts the iminium ion adduct (step 3)

Reversing Neuromuscular Blockade without Nerve Stimulator Guidance in a Postsurgical ICU-An Observational Study

We aimed to determine if not using residual neuromuscular blockade (RNB) analysis to guide neuromuscular blockade reversal administration in the postsurgical ICU resulted in consequences related to residual weakness. This single-center, prospective study evaluated 104 patients arriving in a postcardiac surgical ICU. After demonstrating spontaneous movement and T \u3e 35.5 °C, all patients underwent RNB evaluation, and neostigmine/glycopyrrolate was then administered. When patients later demonstrated an adequate Rapid Shallow Breathing Index, negative inspiratory force generation, and arterial blood gas values with minimal mechanical ventilatory support, RNB evaluation was repeated in 94 of the 104 patients, and all patients were extubated. Though RNB evaluation was performed, patients were extubated without considering these results. Eleven of one hundred four patients had not achieved a Train-of-Four (TOF) count of four prior to receiving neostigmine. Twenty of ninety-four patients demonstrated a TOF ratio ≤ 90% prior to extubation. Three patients received unplanned postextubation adjunct respiratory support-one for obvious respiratory weakness, one for pain-related splinting compounding baseline disordered breathing but without obvious benefit from BiPAP, and one for a new issue requiring surgery. Residual neuromuscular weakness may have been unrecognized before extubation in 1 of 104 patients administered neostigmine without RNB analysis. ICU-level care may mitigate consequences in such cases

Computational study of iminium ion formation: effects of amine structure

D. functional calcns. are used to explore the formation of iminium ions from secondary amines and acrolein and the subsequent reactivity of the resulting iminium ions. After establishing a feasible profile for this reaction in simulated exptl. conditions, we focus on the effect of variation in amine structure on calcd. barriers. This anal. shows that incorporation of a heteroatom (N or O) in the α-position to the reactive amine results in significantly reduced energy barriers, as does an electron-withdrawing group (carbonyl or thiocarbonyl) in the β-position. Electron d. anal. is used to monitor reactions at a detailed level, and to identify important intermol. interactions at both min. and transition states. Barriers to reaction are linked to calcd. proton affinities of secondary amines, suggesting that the relative ease of protonation-deprotonation of the amine is a key property of effective catalysts. Moreover, barriers for subsequent Diels-Alder reaction of iminium ions with cyclopentadiene are lower than for their formation, suggesting that formation may be the rate detg. step in the catalytic cycle

A recyclable fluorous organocatalyst for Diels-Alder reactions

Chiral fluorous imidazolidinone catalyst 2 provides consistently high enantioselectivities in Diels-Alder reactions of dienes and α,β-unsaturated aldehydes. The catalyst can be readily separated from the reaction products by fluorous solid-phase extraction, and recovered in excellent purity for direct reuse. © 2006 Elsevier Ltd. All rights reserved