high enantioselectivity and good yield were observed for aryl methyl ketones, with a modest drop in enantioselectivity for electron-poor substrates. Other aryl ketones gave rise to good to excellent e.r.'s, as highlighted by substrate 2h. Heteroaromatics were also well tolerated under the reaction conditions, with thiophene-and furan-derived ketones undergoing highly enantioselective propargylation reactions (2i and 2j). Additionally, an a,b-unsaturated ketone was an excellent substrate for enantioselective propargylation, leading to a 95:5 e.r. (2p). In the case of aliphatic ketones, the catalyst selected on the basis of steric differentiation, giving higher e.r.'s with increased steric bulk on a single side of the ketone (2l to 2o). An e.r. of 85:15 observed for 2-hexanone (2l) is relatively impressive, considering that the catalyst is differentiating a methyl from an n-butyl group. Groups with substitution at the a-position of the ketone substantially enhanced the e.r.'s, as highlighted by ketones with a cyclohexyl (96:4 e.r., 2n) and a t-butyl group (98:2 e.r., 2o). Furthermore, a g-butyrolactone (2q) could be synthesized with a good e.r. from propargylation of an aliphatic ketone with a pendant ester. Our data suggest that steric-electronic correlations provide a means for efficient optimization of a catalytic system and are evidence for a synergistic relationship between these two classically independent variables in reactions. This is especially attractive for optimizing reactions with limited detailed mechanistic and structural understanding and, considering that the modeling is tied to basic physical organic precepts, a greater understanding of the underlying features of asymmetric catalysis should result. The application of this method is not limited to asymmetric catalysis but can potentially be applied to broad areas of chemistry dependent on evaluating the interplay of two (or more) effects on a reaction outcome. We identified individual-level diurnal and seasonal mood rhythms in cultures across the globe, using data from millions of public Twitter messages. We found that individuals awaken in a good mood that deteriorates as the day progresses-which is consistent with the effects of sleep and circadian rhythm-and that seasonal change in baseline positive affect varies with change in daylength. People are happier on weekends, but the morning peak in positive affect is delayed by 2 hours, which suggests that people awaken later on weekends.
In REF , Golder and Macy collected 509 million English tweets from 2.4 million users in Twitter and disclosed the individual-level diurnal and seasonal mood rhythms in cultures across the globe.
Diurnal and Seasonal Mood Vary with Work, Sleep, and Daylength Across Diverse Cultures
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