Photoassisted Synthesis of Complex Molecular Architectures: Dearomatization of Benzenoid Arenes with Aza‐o‐xylylenes via an Unprecedented [2+4] Reaction Topology

A new method was developed for the photoinduced dearomatization of arenes through an intramolecular cycloaddition with aza‐o‐xylylenes generated by excited‐state intramolecular proton transfer (ESIPT) in the readily available photoprecursors. The [2+4] topology of this cycloaddition is unprecedented for photo‐dearomatizations of benzenoid aromatic carbocycles. It provides rapid access to novel heterocycles, cyclohexadieno‐oxazolidino‐quinolinols, as valuable synthons for a broad range of post‐photochemical transformations.     

2,6,7-trithiabicyclo[2.2.2]octanes as promising photolabile tags for combinatorial encoding

The adducts of trithiabicyclo[2.2.2]octane (TTBO) and carbonyl compounds undergo efficient photoinduced fragmentation with quantum yields comparable to that of dithiane adducts. The effect of the third sulfur on the stability of the respective radical cations and radicals is examined computationally and experimentally in a laser flash photolysis study. A straightforward synthetic approach to a variety of 4-substituted trithiabicyclo[2.2.2]octanes from 3-bromo-2,2-bis(bromomethyl)propanol is developed, making a diverse set of mass-differentiated photolabile tags readily available for combinatorial encoding.     

A pennorth of grossone

Some comments are given on the so-called “Infinity Computer” and grossone by Ya. D. Sergeyev.     

Nonstandard analysis: Its creator and place

This is a biographical sketch and tribute to Abraham Robinson on the 95th anniversary of his birth with a short discussion of the place of nonstandard analysis in the present-day mathematics.     

Simplified x-ray diffraction method for determining the framework composition of high-silica faujasites

Conclusions The x-ray diffractograms of high-silica Y zeolites have four reflections whose relative intensities correlate with the framework composition, and this relationship can be used to evaluate the Si/Al ratio in Y zeolites.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1497–1501, July, 1988.     

Beyond the Dimer and Trimer: Tetraspiro[2.1.25.1.29.1.213.13] hexadecane‐1,3,5,7‐tetraone—the Cyclic Tetramer of Carbonylcyclopropane

Tetraspiro[2.1.2⁵.1.2⁹.1.2¹³.1³]hexadecane‐1,3,5,7‐tetraone 4 , a unique tetraketone containing a cyclooctane core and four spiroannelated cyclopropane moieties, represents the previously unknown cyclotetramer of carbonylcyclopropane. For this purpose oxidation of the parent polyspirocyclic hydrocarbon was examined under various oxidative conditions, and the reactivity of oxidants towards methylene groups of the eight‐membered cycle, activated by adjacent spirocyclopropane rings, was evaluated and contrasted. Whereas the treatment of tetraspirohexadecane with ozone resulted in monooxidation, its reaction with methyl(trifluoromethyl)dioxirane afforded the product of four‐fold oxidation, triketoalcohol 10 . Subsequent oxidation of the latter with Dess–Martin periodinane gave the target tetraketone 4 .     

Photoinduced signal amplification through controlled externally sensitized fragmentation in masked sensitizers

Addition of lithiated dithianes to diaryl ketones, potential electron-transfer sensitizers, disrupts conjugation between the two aromatic moieties, effectively masking the sensitizer. A novel photoamplification strategy is developed based on photosensitized cleavage in such adducts, where each fragmentation event releases more diaryl ketone, capable of sensitization. As a result, mass release of dithianes, triggered with a very small amount of the initiator, is observed. Such amplified release can be made contingent on a molecular recognition event, offering a promising methodology for high throughput bioanalytical applications. The concept is proved with the use of micro- and nanosized polymeric supports, including dendrimers.     

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.