Search

Formal removal of two bonding partners from boranes, BR 3 , yields borylenes, RB, which have been inferred as reactive intermediates in a number of reactions. Phenylborylene (R = C 6 H 5 ; 1) is accessible from phenyldiazidoborane by photochemical extrusion of dinitrogen under matrix isolation conditions. Concomitantly, the nitrene PhNBN is formed via phenyl rearrangement. Here we used a combination of UV/vis, IR, and ESR spectroscopy under cryogenic matrix isolation conditions to investigate the properties and reactivity of phenylborylene. We detected an absorption band of phenylborylene at 375 nm (S 0 → S 2 ) and tentatively assigned the S 0 → S 1 transition to a very weak band at 518 nm. We also show for the first time that an electrophilic borylene such as 1 can react with N 2 reversibly and with CO irreversibly under photochemical conditions. The corresponding photoproducts PhBNN and PhBCO have triplet electronic ground states. Their small E values are in agreement with the linear arrangements Ph-B-N-N and Ph-B-C-O obtained by density functional theory computations. The D values decrease in the series PhNBN > PhBNN > PhBCO and approach the value for phenylcarbene (PhCH). Indeed, the boron center in PhBCO is isoelectronic with the carbene center in PhCH. The compounds are the first examples of boron analogues of diazoalkanes (R 2 CNN) and ketenes (R 2 CCO), and their formation may serve as a demonstration of the high reactivity of phenylborylene.

The generation of 1,2-azaborine (4), the BN-analogue of ortho-benzyne, was recently achieved by elimination of tert-butyldimethylchlorosilane under the conditions of flash vacuum pyrolysis. The present investigation identifies by computational means pathways for the thermal isomerization and fragmentation of 1,2-azaborine. The computations were performed using single reference (hybrid/density functional, second order Møller-Plesset perturbation, and coupled cluster theories) as well as multiconfiguration methods (complete active space SCF based second order perturbation theory, multireference configuration interaction, and multiconfiguration coupled electron pair approximation) with basis sets up to polarized triple-ζ quality. The 1,2-azaborine is, despite the distortion of its molecular structure, the most stable C4H4BN isomer investigated. The formation of BN-endiyne isomers is highly unfavorable as the identified pathways involve barriers close to 80 kcal mol(-1). The concerted fragmentation to ethyne and 2-aza-3-bora-butadiyne even has a barrier close to 120 kcal mol(-1). The fragmentation of BN-enediynes has energetic requirements similar to enediynes., (© 2015 Wiley Periodicals, Inc.)

The BN analogue of ortho-benzyne, 1,2-azaborine, is generated by flash vacuum pyrolysis, trapped under cryogenic conditions, and studied by direct spectroscopic techniques. The parent BN aryne spontaneously binds N2 and CO2, thus demonstrating its highly reactive nature. The interaction with N2 is photochemically reversible. The CO2 adduct of 1,2-azaborine is a cyclic carbamate which undergoes photocleavage, thus resulting in overall CO2 splitting., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Introduction: Rehabilitation in ambulatory heart groups has become a well established part of comprehensive cardiac treatment in Germany. Identifying patients at risk for cardiovascular symptoms is important for the efficiency and safety of the program., Methods: Questionnaires were mailed to ambulatory heart groups in the state of Hessen, Germany, and returned by 1935/13 174 (15%) patients, age 65.9 +/- 7.6 years, 1504/1935 (77.7%) males, comprising approximately 674 000 patient exercise hours., Results: 828 symptoms were reported by 538 patients, comprising dyspnea in 330/538 (61.3%), angina pectoris in 80/538 (14.9%), palpitation in 145/538 (27%), tachycardia in 59/538 (11%), dizziness in 152/538 (28.3%), fainting in 6/538 (1.1%), and others in 47/538 (8.7%). Cardiovascular symptoms occurred more frequently in patients presenting with overexertion (43/68 (63.2%), p < 0.0001, RR 4.77 [95% CI 3.01-7.56]), chronic heart failure (115/291 (39.5%) vs 419/1624 (25.8%), p < 0.0001, RR 1.88 [95% CI 1.45-2.43]), lower exercise capacity (1.49 +/- 0.4 vs 1.59 +/- 0.5 W/kg body weight, p = 0.0002, mean difference -0.096 [95% CI (-0.146) -(-0.046)]), hypertension (269/ 854 (31.5%) vs 266/1068 (24.9%), p = 0.001, RR 1.39 [95% CI 1.14-1.69]), and hyperlipidemia (280/ 907 (30.9%) vs 255/1015 (25.1%), p = 0.005, RR 1.33 [95% CI 1.09-1.63]). Cardiovascular symptoms were more frequent in women (141/431(32.7%) vs 397/1503 (26.4%), p = 0.01, RR 1.35 [95% CI 1.08-1.71]). Overexertion (p < 0.0001), heart failure (p = 0.003), and hypertension (p = 0.05) are significant independent predictors of cardiovascular symptoms, while female gender (p = 0.06), and hyperlipidemia (p = 0.07) are not as significant. Previous myocardial infarction and diabetes had no statistical significant impact on cardiovascular symptoms., Conclusion: Patients likely to experience cardiovascular symptoms in ambulatory rehabilitation can be identified by their medical history and perceived exertion.

Introduction: Rehabilitation in ambulatory heart groups has become well established in comprehensive cardiac care. The prevention of injuries is critical to the safety and efficiency of the program., Methods: Questionnaires were mailed to the ambulatory heart groups in the state of Hessen, Germany and answered by 1935/13 000 (15 %) patients (65.9 +/- 7.6 years, 1504/1935 (77.7 %) men covering approximately 674,000 patient exercise hours., Results: Seventy-eight of the 106 (73.6 %) injuries reported occurred during games encompassing 28/106 (26.4 %) strains, 24/106 (22.6 %) bruises, 17/106 (16.0 %) sprains, 11/106 (10.4 %) bone fractures, 6/106 (5.7 %) ruptured tendons, 8/106 (7.5 %) ruptured muscles, 3/106 (2.8 %) ruptured ligaments, and 9/106 (8.5 %) miscellaneous. The injury risk was neither related to the cardiovascular diagnosis, the prevalence of diabetes, body mass index, previous sport experience, duration of participation in rehabilitation programs, nor to the participant's age. Patients on anticoagulants or after cardiovascular surgery had no excess risk. Gender was the only independent predictor of injuries. In men the overall incidence of injuries was higher (97/1504 [6.4 %]) than in women (9/431 [2.1 %]), p < 0.0005) while the severity was higher in women (6/9 = 66.7 % vs. 22/97 = 22.7 % p < 0.001). The injuries were treated by elastic bandages or band-aids in 69/106 (65.1 %), by splinting in 4/106 (3.8 %), by local injections in 4/106 (3.8 %), by massages in 3/106 (2.8 %), and by others in 26/106 (24.5 %). Five of the 106 (4.7 %) injuries required hospitalization., Conclusion: The traumatologic risk in the rehabilitation of cardiovascular outpatients is associated with a low incidence of injuries.