Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• the cavitand, which enhanced the selectivity of the monoester product 45. Similarly, the monohydrolysis of α,ω-diisocyanate 46 was achieved using the water-soluble cavitand D (Figure 13b) [77]. The residual isocyanate group was buried deep in the cavity of D and protected from further hydrolysis. The

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• , urethanes and isocyanates point inward (Scheme 9). This observation was confirmed by X-ray crystallography as well as calculations at the B3LYP/6-31G** level [38][39]. The tert-butyl groups provide steric protection to the exo sides of the molecules, making the diisocyanate stable at ordinary temperatures

• tetraoxaadamantanes. Inward-pointing isocyanate, urethane and carbamate groups in bisdioxines. The diisocyanate is obtained by Curtius and Hofmann rearrangements of the diazides and diamides [38][39]. Microwave-assisted tetraoxaadamantane formation. Cyclic bisdioxine ester derivative 34 forming a single mono

Detection of therapeutic radiation in three-dimensions

• John A. Adamovics

Beilstein J. Org. Chem. 2017, 13, 1325–1331, doi:10.3762/bjoc.13.129

• typically a mixture of dicyclohexylmethane-4,4'-diisocyanate (HMDI, Figure 2) and it’s polyether prepolymer (CAS 531-70-03-9). While part B is a polyether or polyester polyol mixture which is proprietary [46]. Other aliphatic diisocyanate also used are 1,6-hexamethylene diisocyanate (HDI) and isophorone

• diisocyanate (IPDI) [47]. The polymerization reaction is exothermic and the rate of curing is dependent on the temperature, concentration of reactive groups, total volume of the reactants and type and concentration of metal catalyst. A number of metals have been studied in the polymer reaction but the most

• adventitious moisture with the diisocyanate. The degree of hardness of the dosimeter can be contolled by the type of polyol and catalyst utilized. Hardness ranging from rigid to tissue-like can be achieved [46]. The urethane reaction also tolerates up to relatively high addition (50%) of various solvents such

Extrusion – back to the future: Using an established technique to reform automated chemical synthesis

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 65–75, doi:10.3762/bjoc.13.9

• viscosity, rheology and the kinetics of formation also. The authors report that a reaction between 4,4’-diphenylmethane diisocyanate, polycaprolactonediol and 1,4-butanediol takes place in a twin screw extruder, employing a screw speed of 15 rpm and a temperature of 60 °C [25]. This transformation was

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• example of a catalytic aza-Wittig reaction as part of their research on phosphine oxide-catalyzed carbodiimide synthesis (Scheme 13) [30]. In their reaction they used phosphine oxide 40 as the catalyst in the reaction between diisocyanate 41 and benzaldehyde (42, 2 equivalents) to form diimine 43 and

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• -based polymers The reaction of β-CD with diphenyl carbonate (DPC) or hexamethylene diisocyanate (HDI) afforded crosslinked, insoluble polymers. We synthesized these systems and tested as sequestering agents for naringin [31]. These syntheses were carried out under US with shorter reaction times and

• synthetic procedure to graft viscose using a diisocyanate cross-linker was reported (Scheme 6) [32]. Sonochemical reticulation with HDI was used in the preparation of a new series of solid cross-linked α-, β- and γ-CD-based catalysts containing Cu(I) or Pd(II) [33]. Sonication breaks up intermicellar

• , while nanostructure size and shape were regulated according to the structure of the CD-PG dendrons [75]. CD-based polymers can be easily prepared under MW. Biswas et al. have prepared a number of macromolecular structures from α-, β-, γ-CDs by crosslinking reactions with toluene diisocyanate and

Preparation of Pickering emulsions through interfacial adsorption by soft cyclodextrin nanogels

• Shintaro Kawano,
• Toshiyuki Kida,
• Mitsuru Akashi,
• Hirofumi Sato,
• Motohiro Shizuma and
• Daisuke Ono

Beilstein J. Org. Chem. 2015, 11, 2355–2364, doi:10.3762/bjoc.11.257

• -active property. Results: CD nanogels were prepared by crosslinking heptakis(2,6-di-O-methyl)-β-cyclodextrin with phenyl diisocyanate and subsequent immersion of the resulting polymer in water. A dynamic light scattering study shows that primary CD nanogels with 30–50 nm diameter assemble into larger CD

• . We have previously reported urethane-crosslinked CD polymers, which were prepared by reacting heptakis(2,6-di-O-methyl)-β-cyclodextrins (DM-β-CDs) with aromatic diisocyanates such as 4,4’-methylenebis(phenyl isocyanate) (MDI) and 1,4-phenylene diisocyanate (PDI) [18]. Although MDI- or PDI-crosslinked

• to use. Anhydrous N,N-dimethylformamide (DMF) and 1,4-phenylene diisocyanate (PDI) were purchased from Wako Pure Chemical Industries, Ltd. (Japan). Toluene and n-dodecane were purchased from Kanto Chemical Co., Ltd. (Japan). Fluorescein-4-isothiocyanate was purchased from Dojin Chemical Co. Ltd

Molecular cleft or tweezer compounds derived from trioxabicyclo[3.3.1]nonadiene diisocyanate and diacid dichloride

• Gert Kollenz,
• Ralf Smounig,
• Ferdinand Belaj,
• David Kvaskoff and
• Curt Wentrup

Beilstein J. Org. Chem. 2015, 11, 1–8, doi:10.3762/bjoc.11.1

• Abstract The structures of two derivatives of the bisdioxine diisocyanate 1, the bisurea 4 and the biscarbamate 5, are established by X-ray crystallography and DFT calculations. These compounds possess endo,endo structures, in the case of the bisurea 4 with two nearly parallel pendant chains. The X-ray

• ability to extract some alkali, alkaline earth and rare earth metal ions. Keywords: carbamates; crown ethers; diisocyanate; isocyanate; ureas; Introduction The synthesis of the surprisingly stable, monomeric diisocyanate 1 (Figure 1) was reported recently [1]. This and several other derivatives of the

• minima [1]. Optimization of the endo,exo structure leads to ring opening to a new diisocyanate (Scheme 1). Therefore, it is of some importance to ascertain the actual molecular structures of compounds of this type by X-ray crystallography. Here we report the X-ray crystal structures of two derivatives of

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• BMPDPTH and 1,4-phenylene diisocyanate (PDI) to provide polyimide 120 and polyurea 121 [50][51][52][53]. Ye also investigated the similar (bi)imidazole-derived polymers 122 and 123 (X = OH) with a polyuretane backbone generated after copolymerization with 3,3’-dimethoxy-4,4’-biphenylene diisocyanate

• polyuretane and polyester by solution copolymerization with tolylene-2,4-diisocyanate (TDI), (2-methoxy)terephthaloyl dichloride [(M)TPC], and isophthaloyl dichloride (IPC) to afford nonlinear optical polymers 135–140. Polymers 141–143 were synthesized by AIBN-promoted polymerization of the methacrylate

Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers

• Daniel Crespy and
• Katharina Landfester

Beilstein J. Org. Chem. 2010, 6, 1132–1148, doi:10.3762/bjoc.6.130

• such as 1,12-dodecanediol, bisphenol A, and/or neopentyl glycol, and the slow reacting isophorone diisocyanate (IPDI) were reacted in miniemulsion droplets [12]. Similar reactions were performed but in the presence of an organotin catalyst [101]. Relatively high apparent molecular weight polyurethane

• could be obtained. The molecular weight could be increased by the use of an organotin catalyst, a solvent in the dispersed phase and an excess of diisocyanate compared to diol. Instead of synthetic polyols, it is possible to employ polyols from renewable resources to synthesize polyurethane in

• diisocyanate component [104]. The particles were used to encapsulate nimodipine, a calcium channel blocker. A popular method to form polyurethane latexes in direct aqueous miniemulsions is to dissolve a reactive preformed prepolymer in the dispersed phase and subsequently carry out the polyaddition. The