Two steps one pot process for the conversion of dimethylfuran to pyrrole compounds with almost null E factor

The replacement of the oil-based chemicals with those derived from biomasses is one of the most exciting challenges of the last decades. For example, 1,4-dicarbonyl compounds have a great importance in chemical synthesis, thanks to their high chemoselectivity and there is an increasing interest for preparing them from biomasses. In particular, 2,5-hexanedione could be synthesized starting from lignocellulosic sources, through the acid-ring opening reaction of 2,5-dimethylfuran as the bio-based feedstock.[1] The reaction of 2,5-hexanedione and a generic primary amine leads to pyrrole compounds. Many examples have been reported by some of the authors.[2] In this work a sustainable process for the preparation of pyrrole compounds starting from a bio-based reagent has been developed. The selected starting material was 2,5-dimethyl furan. In this work, the ring opening reaction of 2,5-dimethylfuran was optimized by tuning parameters such as the amount of water, type and amount of acid, time and temperature. 2,5-hexanedione was obtained with a high yield (95%) without the need of purification. Then, different primary amines, in particular biosourced, have been used to prepare a variety of pyrrole compounds, with high yield (at least 90%) and with high carbon efficiency, without producing waste. The pyrrole compounds have then been used for the functionalization of a nanosized graphite, promoting the exfoliation to few layers graphene

Concomitant dehiscences of the temporal bone: a case-based study

Otic capsule dehiscences create a pathological third window in the inner ear that results in a dissipation of the acoustic energy consequent to the lowered impedance. Superior semicircular canal dehiscence (SSCD) was identified by Minor et al. in 1998 as a syndrome leading to vertigo and inner ear conductive hearing loss. The authors reported the relation between the dehiscence and pressure- or sound-induced vertigo (Tullio phenomenon). The pathophysiology of this entity still remains controversial. Prevalence rates of SSCD in anatomical studies range from 0.4 to 0.7 % with a majority of patients being asymptomatic. The observed association with other temporal bone dehiscences, as well as the propensity toward a bilateral or contralateral near-dehiscence, raises the question of whether a specific local bone demineralization or systemic mechanisms could be considered. The present report regards a case of a patient with a previous episode of meningitis, with a concomitant bilateral SSCD and tegmen tympani dehiscence from the side of meningitis. The patient was affected by dizziness, left moderate conductive hearing loss and pressure/sound-induced vertigo. Because of disabling vestibular symptoms, the patient underwent surgical treatment. A middle cranial fossa approach allowed to reach both dehiscences on the symptomatic side, where bone wax and fascia were used. At 6 months from the procedure, hearing was preserved and the vestibular symptoms disappeared

Bionanocomposites based on chitosan and few layers graphene. The effect of tailor-made functionalization

Bionanocomposites are an emerging class of material. They are designed and developed to achieve advanced structural and functional properties, by using biobased polymers. Among the bio-polymers, focus is on chitosan (CS), poly (N-acetyl-D-glucosamine), a copolymer of [1,4]-linked 2-acetamido-2-deoxy-D-glucopyranose and 2-amino-2-deoxy-D-glucopyranose. Research is steadily increasing on bionanocomposites with graphene and graphene related materials. It is here presented a research on bionanocomposites based on CS and graphene layers (G). Particular focus of the research was on the integration of the graphene layers in the nanocomposite. Materials were prepared based on the supramolecular interaction between CS and G. The core of the research was then on the edge functionalization of the layers. OH groups were added through the cycloaddition reaction with a biosourced pyrrole compound, serinol pyrrole (SP), carried out with the help of either thermal or mechanical energy, with an atom efficiency up to 96% and a very low E Factor. The preparation of CS/G adducts was very simple, even by using only mortar and pestle. OH groups were also added to the G edges by performing the reaction of G with KOH. The Reimer-Tiemann reaction on the G-OH adduct led to the introduction of aldehydic groups, which promote the crosslinking of CS. The CS/G adducts were characterized by means of wide angle X-ray diffraction, scanning and transmission electron microscopy, Fourier transform infrared, X-ray photoelectron and Raman spectroscopies. Thermal stability of the composites was studied by thermogravimetric analysis. Carbon papers and aerogels were prepared, studying the flexibility and the stability in various solvents in a wide pH range

Facile Edge Functionalization of Graphene Layers with a Biosourced 2-Pyrone

Edge functionalization of graphene layers is of great interest in the field of materials chemistry: the properties of graphene are substantially unaltered and its compatibility and chemical reactivity with various environments can be tuned. In this work, edge functionalization of graphene layers was performed with a 2-pyrone, ethyl 3-hydroxy-2-oxo-2H-pyran-6-carboxylate (Pyr-COOEt). 2-Pyrones are C-6 unsaturated heterocyclic sugar derivatives and are intriguing building blocks for the preparation of innovative chemical structures. Sodium 3-acetoxy-2-oxo-2H-pyran-6-carboxylate was prepared starting from mucic acid, in a one-pot synthesis with a yield of about 74%, and was then transformed into the acid and then into ethyl ester derivatives. The adduct of Pyr-COOEt with a high surface area graphite (HSAG) was obtained by simply mixing and donating energy, either thermal or mechanical. The functionalization yield was estimated from thermogravimetric analysis (TGA) data and was found to be up to 91%. The adducts were characterized by Fourier transform infrared and Raman spectroscopies and wide-angle X-ray diffraction. The presence of pyrone in the adduct was clearly detected in the IR spectra, and the bulk structure of the graphitic substrate was found to be substantially unaltered by the functionalization reaction. The experimental findings suggest that the edge functionalization of the graphene layers occurred. Stable water dispersions of HSAG/Pyr adducts were prepared and studied through ultraviolet-visible analysis. Aggregates of few-layer graphene were obtained by mild sonication and centrifugation, as revealed by high-resolution transmission electron microscopy. This paper shows that a biobased molecule can be used for selectively decorating the edges of graphene layers, with oxygenated functional groups having a defined chemical structure and avoiding the use of oil-based, dangerous, and even noxious ingredients. The most plausible interpretation for the formation of the HSAG adduct with 2-pyrone seems to be the cycloaddition reaction between the edges of the graphitic substrate and the unsaturated biomolecule. Such a functionalization appears to be suitable for a scale up and paves the way for the preparation of a variety of derivatives

Sustainable materials for tyres. 3. Biobased secondary accelerators for silica based compounds

It is well known the sentence by Charles Goodyear: “There is probably no other inert substance the properties of which excite in the human mind an equal amount of curiosity, surprise and admiration”. He was referring to entropic elasticity. To have such a property, a rubber has to be crosslinked. Compounds for tyre application are crosslinked with sulphur base system. In particular, when silica is the reinforcing filler, the sulphur vulcanization package is composed by orthorhombic sulphur, at least a sulphenamide and a secondary accelerator, such as guanidines, thiurames, mercaptobenzothiazoles and others, in order to boost the reaction. In this work, innovative chemicals were developed as secondary accelerators for silica based rubber compounds, starting from 2-amino-1,3-propanediol (known as serinol), which was used as such or as the starting building block for the preparation of imines. Imines, also known as Schiff bases, are traditionally synthesized from the reaction of primary amines with aldehydes or ketones, in the presence of an acid catalyst. This work had the aim to develop synthetic strategy to perform reactions for the synthesis of imines, by adopting reaction conditions inspired to the basic principles of green chemistry, in the absence of any solvent and catalyst, with aldehydes and ketones such as: acetone, cinnamaldehyde and camphor. Serinol and serinol derivatives were thus used as secondary accelerators for the vulcanization of compounds based on silica and diene elastomers. Their behaviour was compared with that of diphenyl guanidine. Kinetics of crosslinking was studied, in the presence and in the absence of fillers. Dynamic-mechanical properties of the compound were determined. Extractability of vulcanizers from the compound was as well investigated

Thulium laser in stapedotomy surgery

Background: Revolix JR (Thulium) laser use in stapedotomy surgery has previously raised issues regarding its thermal effects on the vestibular area with production of acoustic shock waves which may result in permanent complications. Objectives: To evaluate the efficacy and safety of the Thulium laser use in stapedotomy and its long-term effect on the clinical and audiological results. Study design: Retrospective case series study. Settings: All surgeries were performed at a single Otologic Center of a tertiary University Hospital. Subjects: 148 otosclerosis patients, with ages ranging from 18 to 78 years, were divided into two groups; group A included 62 patients, and group B included 86 patients. Intervention: In all patients, the reversal-stapedotomy technique was used. In group A, multiple overlapped 4 W Thulium shots, with a 15-seconds interval between them, were used. In group B, one shot followed by regularization with a manual perforator was used. The main outcome measures: The preoperative and the postoperative threshold as pure tone average (PTA4) were evaluated along with eventual intraoperative (footplate cracking and stapedectomy) and the postoperative complications (SNHL, vertigo, and tinnitus). Results: a statistically significant improvement of the ABG in both groups was achieved. ABG closure (< 10 dB) was 87.1% of patients in group A and 89.5% of patients in group B. Intraoperative complications were more observed in group B (p-value=0.038), while the postoperative complications occurred more in group A (p-value=0.017). Conclusions: According to our experience on a relatively large number of cases, the Thulium laser is a safe tool to be used in stapedectomy either by multiple shots or by single shot plus manual perforator. The use of this tool showed to be effective in improving functional hearing with minimum, nonsignificant rate of complications that were not affecting the inner ear function

On the battery life of a totally implantable active middle ear device: a retrospective study in a single implanting center

Background: Totally-implantable active middle ear devices (AMED) rely on a non-rechargeable battery encased with the implantable sound processor that needs to be replaced with a minor surgical pro- cedure after its depletion. Objectives: This study aimed to investigate the most significant factors affecting the implant’s bat- tery life. Materials and Methods: The implanted subjects (29 patients) were divided into three groups; group A with 17 patients who underwent one battery change surgery; group B with ten patients who under- went two battery changes; and group C with two patients and three surgeries. The battery life was put in correlation with several variables, including daily use and the auditory threshold. Results: The battery life ranged from 26 to 67 months, with a mean of 48.93 ± 13.47. Pearson’s correl- ation coefficient revealed that the battery life was statistically correlated only with the mean post- implantation bone conduction thresholds (p-value <.0001). Conclusions: Although the non-rechargeable battery system of the AMED under study overcomes the drawbacks of daily charging, it needs to be surgically changed after its depletion. The different rates of battery life were shown to mainly depend on the post-implantation BC thresholds, which in some cases showed a deterioration concerning the pre-implanting values