Detecting solid-state reactivity in 10-hydroxy-10,9-boroxophenanthrene using NMR spectroscopy

Solid-state NMR spectroscopy and computational methods are used to probe the transformation of 10-hydroxy-10,9-boroxophenanthrene to its corresponding anhydride in the solid state. DFT calculations are used to assist the assignment of the NMR spectra of both these boron-containing heteroaromatic compounds, in solution and in the solid state. Solid-state NMR spectroscopy reveals that the dehydration of crystalline 10-hydroxy-10,9-boroxophenanthrene proceeds at relatively low temperatures—a transformation, that is, undetectable by X-ray diffraction and gravimetric analysis. Computational methods are used to elucidate a plausible reaction pathway for this transformation and to explain its detection only by NMR methods.     

Interrupted oligomerization revisited: simple and efficient one-pot multicomponent approach to versatile synthetic intermediates

A novel multicomponent reaction allowing for a one-pot formation of three carbon-carbon bonds has been developed. It is based on in situ generation and anionic dimerization of methylenedithiane and produces a versatile synthetic equivalent of 4-hydroxy-1,3-alkanediones which, among other things, offers expeditious one-pot access to 3(2H)-furanones.     

β-Bromodifluoromethyl β-enaminoketones: versatile synthetic intermediates for synthesis of CF2-containing compounds

A series of N-aryl β-bromodifluoromethyl β-enaminoketones were regioselectively synthesized in good yield by the reaction of N-aryl bromodifluoroacetimidoyl chlorides with methyl ketones. β-Bromodifluoromethyl β-enaminoketones smoothly cyclized to give a novel class of cyclic (2,2-difluoro-5-phenyl-furan-3-ylidene)-aryl-amines under basic condition. An intramolecular halophilic substitution mechanism was proposed.     

A versatile synthetic approach to periodic mesoporous organosilicas

A synthetic protocol for the preparation of a variety of high-quality periodic mesoporous organosilicas (PMOs) is presented. These nanostructured organosilicas have been synthesized by the acid-catalyzed hydrolysis and condensation of bis(triethoxysilyl) precursors containing different organic bridging groups. Polyoxyethylene(10) stearyl ether (Brij 76) is employed as the structure director using the surfactant template approach. Methylene, ethylene, ethenylene, and phenylene-bridged PMOs have been synthesized. Surfactant extraction is accomplished by refluxing the mesoscopic composite precipitates in acidified ethanol. The resulting PMOs have been characterized by nitrogen gas sorption, powder X-ray diffraction, ¹³C and ²⁹Si solid-state NMR, and high-resolution thermogravimetric analysis. These organosilicas exhibit large surface areas, narrow pore size distributions, and large total pore volumes. This is the first report of a synthetic protocol with the versatility to make high-quality PMOs containing aliphatic, aromatic, or olefinic carbon functional groups. This versatility is discussed in terms of template and precursor structures under the acidic reaction conditions.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00396-003-1004-0     

A versatile synthetic path to thiol containing polysiloxanes

A synthetic strategy to polydimethylsiloxanes and polymethylsiloxanes containing thiol functions as end‐ or side‐groups, respectively, is presented. Such polymers are important starting materials for elastomeric networks and postpolymerization modifications. The synthesis starts either with vinyl end‐functionalized polydimethylsiloxanes or with polymethylvinylsiloxanes. The vinyl groups are reacted either with thioacetic acid or with a thioacetic acid/butanethiol mixture via a UV‐initiated thiol‐ene reaction to form the respective thioester quantitatively within few minutes. The thioesters are subsequently deprotected to the respective thiols by reduction with LiAlH₄. The resulting thiol containing polysiloxanes can be used for the formation of networks or another functionalization. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2940–2948     

A facile one-pot synthesis of acyclic β-enamino ketones, an important class of versatile synthetic intermediates

A one-pot sequential process consisting of nucleophilic substitution of the lithiated acetylides with Weinreb amides followed by a Michael reaction of the extruded N-methoxy-N-methylamine after quenching with saturated NH₄Cl, provided β-enamino ketones in high yield and in a single geometrical isomeric form. It has been demonstrated that this method is applicable to a wide variety of such amides and to different acetylides.     

A straightforward and versatile synthetic approach to 1-azabicyclic alkaloids

A very straightforward route to 1-azabicyclo alkaloid scaffolds with several ring sizes is reported. The final bicyclic structures were built through a synthetic scheme that involved (i) the construction of dienic 4-piperidone systems by an imino-Diels-Alder reaction between aminotrienes and N-omega-vinylimines, in the presence of Yb(OTf)(3), and (ii) the ring-closing metathesis reaction of these cyclic dienes, under the influence of the first-generation Grubbs' Ru-complex catalyst. During this investigations, various polysubstituted azabicyclic ring skeletons, including several examples of the quinolizidine alkaloids, are reported, and their relative stereochemistry is adequately discussed.     

Aminohydroxyacetone synthons: versatile intermediates for the organocatalytic asymmetric aldol reaction

A practical method for the synthesis of 1,3-aminohydroxyacetone synthons was developed, and their utility in the organocatalytic asymmetric aldol reaction was demonstrated in a short synthesis of aza-sugars.     

CoIIIcorrole: versatile synthetic methods and wide range of applications

Journal of Inclusion Phenomena and Macrocyclic Chemistry - This review introduces the synthesis, properties and applications of CoIIIcorroles. The synthesis methods are containing A2B type, A3...     

Azabicycloalkenes as synthetic intermediates: application to the preparation of diazabicycloalkane scaffolds

[reaction: see text] A general method to synthesize bicyclic dipeptide mimetics is reported. Key intermediates are azabicycloalkenes 9 and 17, which are prepared via Diels-Alder reactions and subsequent mild deprotection. These unsaturated bicyclic heterocycles are versatile intermediates for different dipeptide mimetics of the aza- and diazabicycloalkane type, which is demonstrated by the synthesis of diazabicycloalkanes 11 and 19 in only 3-6 steps and good overall yield.     

New synthetic approach to atypical retinoids: application of a versatile annulation procedure

A new approach to an atypical retinoid is presented. The C₁₅ skeleton was built up by exploiting a step-by-step sequence: the C₉ fragment of an intermediate was homologated by reaction with a C₄ phosphorane, and then submitted to a benzannulation reaction. The last two carbon atoms were inserted by a Wittig reaction with the C₂ phosphorane of ethyl bromoacetate. Manipulation of functional groups was then performed.     

General synthetic approach to bicyclo[9.3.0]tetradecenone: a versatile intermediate to clavulactone and clavirolides

An efficient and stereoselective approach to the bicyclo[9.3.0]tetradecenone core structure of clavulactone starting from readily and abundantly available 2-methyl-1,3-cyclopentandione employing microbial desymmetrization and cyanohydrin alkylation as the key steps is described. The synthetic route described herein is applicable to the syntheses of the core structures of Clavirolides A-F.     

A novel synthetic route to 2-halo-3,4-dicyanopyridines

2-Bromo-3,4-dicyanopyridine 2 was obtained in moderate yield by reacting 1,1,2,2-tetracyano-3-trimethylsiloxycyclobutane 1 with phosphorus tribromide. Similarly, reaction of 1 with chlorinating reagents such as thionyl chloride and oxalyl chloride led to the corresponding 2-chloro-3,4-dicyanopyridine 3 in 40% yield. A reaction mechanism is suggested.     

Ns strategies: a highly versatile synthetic method for amines

A highly efficient and versatile synthetic method for amines was established using nitrobenzenesulfonamides (Ns-amides) as both a protecting and activating group. The alkylation of N-monosubstituted Ns-amides either proceeded conventionally or under Mitsunobu conditions to provide the N,N-disubstituted sulfonamides, and the Ns group was removed easily with soft nucleophiles via Meisenheimer complexes to give the corresponding secondary amines. The major advantage of this protocol is that both alkylation and deprotection proceed under mild conditions. Thus, with this methodology, the total synthesis of linear and/or macrocyclic natural polyamines can be accomplished efficiently.     

Homoatomic P --> P coordination: a versatile synthetic approach to polyphosphorus dications

Polyphosphorus dications have been synthesised and comprehensively characterised as diphosphine (dppe, dmpe and dpph) linked Ar2P+ Lewis acids (Ar = C6H5); this application of unique homoatomic coordination chemistry provides important building blocks for extended systems.