ABSTRACT
Direct assembly of complex fluorinated motifs from simple fluorine sources is an attractive frontier of synthetic chemistry. Reported herein is an unconventional protocol for achieving tetrafluoroisopropylation by using commercially available CF2HSO2Na as a convenient source of the tetrafluoroisopropyl [(CF2H)2CH] group, which finds widespread applications in life science and material science. Visible-light-induced hydrotetrafluoroisopropylation of alkenes and carbotetrafluoroisopropylation of alkynes have been thus developed. Various structurally diverse α-tetrafluoroisopropyl carbonyls and cyclopentanones are selectively constructed under mild conditions. A photocatalytic triple difluoromethylation cascade, driven by consecutive reductive radical/polar crossover processes, leads to the direct assembly of a tetrafluoroisopropyl moiety from CF2HSO2Na. This C1-to-C3 fluoroalkylation protocol provides a practical strategy for the rapid construction of polyfluorinated compounds that are otherwise difficult to access, thus significantly enhancing the boundary of fluoroalkylation chemistry.
ABSTRACT
A radical chain isomerization of N-sulfonyl ynamides to isolable ketenimines is developed, featuring mild reaction conditions, a high efficiency, â¼100% atom economy, a broad substrate scope, and column chromatography-free workup in most cases. Meanwhile, an unprecedented dearomatization of furans is achieved by the radical chain isomerization-triggered aza-Claisen rearrangement, providing highly chemo-, regio-, stereo-, and diastereoselective access to functionalized quaternary nitriles.
ABSTRACT
In this paper, we propose a novel unsupervised approach for sequence matching by explicitly accounting for the locality properties in the sequences. In contrast to conventional approaches that rely on frame-to-frame matching, we conduct matching using sequencelet or seqlet, a sub-sequence wherein the frames share strong similarities and are thus grouped together. The optimal seqlets and matching between them are learned jointly, without any supervision from users. The learned seqlets preserve the locality information at the scale of interest and resolve the ambiguities during matching, which are omitted by frame-based matching methods. We show that our proposed approach outperforms the state-of-the-art ones on datasets of different domains including human actions, facial expressions, speech, and character strokes.
ABSTRACT
AIM: There is accumulating evidence that participation in cognitive leisure activities might be related to a reduced risk of cognitive impairment. However, there is no consensus regarding the classification of cognitive leisure activities, and it cannot clearly define each activity and quantitatively evaluate the effect of it. In the present study, we propose a new classification method, and examine the relationship between reclassified cognitive leisure activities and cognitive function. METHODS: The analysis included 4830 participants of the Chinese Longitudinal Healthy Longevity Survey, who were aged >80 years and free of cognitive impairment at 1998. They were followed up six times. Six cognitive leisure activities were mainly grouped into intrapersonal and interpersonal cognitive leisure activity by categorical principal component analysis. Cox proportional hazards analysis was used to evaluate the relationship between reclassified cognitive leisure activities and the risk of cognitive impairment. RESULTS: After a median follow-up period of 16 years, 1763 participants suffered from cognitive impairment (Mini-Mental State Examination score <24). Reading newspapers or books, taking part in some social activities and sometimes playing cards or mahjong were associated with a decreased risk of cognitive impairment (P < 0.05 for all). In multivariable adjusted models, compared with those with lower intensities, the hazard ratios (95% confident intervals) of cognitive impairment were 0.86 (0.74-0.99) and 0.71 (0.60-0.83) for participants with high intensities of intrapersonal and interpersonal cognitive leisure activity, respectively. CONCLUSION: A high frequency of participation in intrapersonal and interpersonal cognitive leisure activities showed a lower risk of cognitive impairment among the oldest-old in China. Geriatr Gerontol Int 2019; 19: 1041-1047.
