Multiple regression analysis of data from field experiments conducted in Alberta at two locations between 1972 and 1983 indicated that there was a significant relationship between yield loss of barley (Hordeum vulgareL.) and wheat (Triticum aestivumL.) and relative time of emergence of wild oat (Avena fatuaL. ♯ AVEFA). At a given wild oat density, percent yield loss increased the earlier wild oat emerged relative to the crops and gradually diminished the later it emerged. However, the magnitude of the yield loss for both species varied with the year. Regression equations based on data pooled over years and locations were developed to provide an estimate of yield loss of barley and wheat due to relative time of wild oat emergence and wild oat density. The information should be considered when barley and wheat losses due to wild oat are being assessed.

We describe the first example of controlled free radical cyclopolymerization of difunctional styrenic monomers. The newly designed monomers are obtained from the introduction of two 4‐vinylbenzyl moieties as malonate or dialkylated malonate esters. The more sterically hindered monomer is particularly efficient in the cyclization and propagation processes, giving cyclopolymers, in diluted solvent conditions, with good yields and degrees of polymerization. In the presence of a suitable RAFT mediator, and, upon careful optimization of the solvent, temperature and monomer concentration, a linear increase in the number average molecular weight with conversion and low polydispersity indexes can be achieved.

Chirality is a powerful tool for the generation of order, directionality, and, as such, of function, in assembled nanoscale chemical devices. Axially chiral binaphthyls have been widely used in organic synthesis; the stability of the enantiomers enables their use as robust chirality inducers and catalysts in asymmetric reactions, and they are nowadays industrially applied in a variety of organic transformations. Applications of these compounds in the field of nanosciences are more recent, and not yet fully explored. The integration of such a robust class of chiral compounds, capable of efficient transfer of stereochemical information, into functional aggregates and nanoarchitectures is of great current interest. We will discuss preeminent examples of applications of these synthons in several fields of nanoscience, such as reticular chemistry, non-linear optical materials and imaging, and liquid crystals.

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We report on a series of novel homologous push-pull compounds, in which identical donor (a dimethylamino) and acceptor (a malonate ester) functionalities endcap crescent PPV fragments, bearing, respectively, 1, 2 and 3 p-phenylenevinylene units in direct linear conjugation (compounds 7-9). The three compounds exhibit striking differences in their linear and nonlinear optical properties. The shorter compound 7 exhibits aggregation-induced emission with a strong luminescence in the solid state (blue emission, photoluminescence quantum yield 38%), and it is nonemissive in solution; the more extended conjugated systems 8 and 9 show classical aggregation-caused quenching in the solid state, while high quantum yield photoluminescence (21 and 93% in toluene) is restored in diluted solutions, through mechanisms involving intramolecular charge transfer in the excited states. EFISH measurements in solutions demonstrate a strong solvent and concentration dependence. As rationalized with the aid of molecular modelling, compounds 8 and, more markedly, 9 aggregate in stable centrosymmetric dimers in solution.

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Reaction of BF3 coordinated N-ethylpyrrolidine with benzophenone, using a preformed complex of s-BuLi and (−)-sparteine for lithiation at −78 °C, affords enantio-enriched R-product (er 85:15). With a warm−cool cycle (−78° → 0°, 2 h, → −78°) prior to electrophile addition the enantioselectivity is reversed. Similarly, in the reaction of BF3-indolizidine complex syn substitution (dr 97:3) occurs but with a warm−cool cycle the syn−anti ratio gets changed to 41:59. These results indicate initial syn lithiation and formation of excess of the anti intermediate on equilibration. DFT calculations at the B3LYP/6-31+G* level show the syn intermediate to be stable in the gas phase, but with the solvent continuum treatment the relative stability shifts toward the anti arrangement and it become more stable in highly polar solvents. These computations also reveal a close contact between Li and boranato fluorine, and its implications for superior effectiveness of BF3 in promoting lithiation of amines are discussed.

[2.2]Paracyclophanes, incorporating functional groups in the aliphatic bridges, suitable for elimination to give [2.2]paracyclophanedienes, are synthesized through a novel approach. It relies on a double Pummerer rearrangement on dithiacyclophane precursors, followed by ring contraction through a photochemical sulfur extrusion, and it is compatible with aryl moieties possessing very different electronic properties.