Siu Yin Lee

Lands Department of The Government of the Hong Kong Special Administrative Region, Hong Kong, Hong Kong

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Publications (18)

  • [Show abstract] [Hide abstract] ABSTRACT: CoII(por) (por = porphyrinato dianion) reacted selectively with isopropyl ketones at the carbon (CO)-carbon (α) bond at room temperature to give high yields of CoIII(por) acyls and the corresponding oxidized carbonyl compounds in up to 89% yields. CoIII(por)OH is proposed to be the C-C bond activation (CCA) intermediate. The stoichiometric reaction is further developed into the photocatalytic CCA using both UV and visible light sources (λ 405 nm). Under ambient conditions, the photocatalytic C-C oxidation of 2,6-dimethylcyclohexanone gives 2-heptanone in up to 24 turnovers in the presence of isopropyl alcohol as the H atom donor and H2O as the oxidant. Various isopropyl ketones successfully undergo photocatalysis.
    Article · Aug 2016 · Organometallics
  • Siu Yin Lee · Shiyu Feng · Kin Shing Chan
    [Show abstract] [Hide abstract] ABSTRACT: The mild and selective aliphatic C(CO)-C(α) bond activation (CCA) of ketones was successfully achieved at room temperature using rhodium(ii) porphyrins in the presence of H2O. Rh(II)(tmp) (tmp = tetrakismesitylporphyrinate dianion) disproportionates in H2O to generate the highly reactive intermediate Rh(III)(tmp)(OH) for cleaving the C-C bond of ketone, giving up to 90% of Rh(III)(tmp)(COR) and the corresponding oxidized carbonyl product in up to 76% yield within 10 min. Substrate scopes cover aliphatic as well as aromatic ketones. Both isopropyl and cyclic ketones worked well.
    Article · Jan 2016 · Dalton Transactions
  • Chen Shen · Siu Yin Lee · Tai Hing Lam · C Mary Schooling
    [Show abstract] [Hide abstract] ABSTRACT: The inverse association of aerobic exercise with death has been well documented. However, evidence on traditional Chinese exercise (TCE) and rate of death in older Chinese is limited. Multivariable Cox regression analysis was used to assess the associations of TCE and other types of physical activity with death from all causes and specific causes in a population-based prospective cohort of 66,820 Chinese persons (≥65 years of age) who were enrolled between July 1998 and December 2001 at all 18 Elderly Health Centers in Hong Kong and followed up until May 31, 2012. During an average of 10.9 years of follow-up, 19,845 deaths occurred. TCE was inversely associated with death from all causes (hazard ratio (HR) = 0.78, 95% confidence interval (CI): 0.74, 0.82), cardiovascular disease (HR = 0.77, 95% CI: 0.70, 0.85), cancer (HR = 0.84, 95% CI: 0.77, 0.92), and respiratory disease (HR = 0.71, 95% CI: 0.63, 0.80) but was not associated with death from accidents (excluding falls) (HR = 0.79, 95% CI: 0.44, 1.42), after adjustment for age, sex, socioeconomic position, alcohol use, smoking, body mass index, and health status. The associations did not vary by amount of TCE. Aerobic exercise had similar inverse associations as TCE, but associations for stretching exercises and walking slowly were less marked. Further studies of TCE are warranted in older Chinese.
    Article · Dec 2015 · American journal of epidemiology
  • [Show abstract] [Hide abstract] ABSTRACT: Background: Obesity was first noted as a risk factor for severe illness associated with pandemic H1N1 infection in 2009, but the relationship between obesity and seasonal influenza remains unclear. Methods: We used data from a population-based cohort comprising 66 820 older (≥65 years) participants with a follow-up period from 1998 to 2012. The impact of influenza activity on respiratory mortality rates was estimated using a Cox proportional hazards model adjusted for comorbidities, meteorological factors, and other co-circulating respiratory viruses. We also tested whether the association of influenza with respiratory mortality varied with obesity and/or health status. As a control outcome, we similarly assessed the association of influenza with deaths from external causes, because these deaths should be unrelated to influenza. Results: Seasonal influenza activity was associated with higher respiratory mortality (hazard ratio [HR], 1.13 for influenza activity in the influenza season vs noninfluenza season; 95% confidence interval [CI], 1.05-1.22). The effect of seasonal influenza was 19% greater in obese individuals than normal-weight individuals (HR, 1.19; 95% CI, 1.01-1.42). The marginally significant and greater effect modification of obesity status on the association between seasonal influenza and respiratory mortality was also observed among older people in good health (HR, 1.35; 95% CI, .97-1.87). No such relations were observed for death from external causes. Conclusions: Obesity aggravates the effect of seasonal influenza on respiratory mortality. Priority for influenza vaccine should be considered for obese older people to decrease the burden of influenza.
    Article · Feb 2015 · Clinical Infectious Diseases
  • [Show abstract] [Hide abstract] ABSTRACT: Background and AimsLarge cohort studies on smoking and mortality in older people are scarce and few studies examined smokers aged 85+ years separately. We estimated the risks of all-cause and cause specific mortality due to smoking in an elderly Chinese cohort in Hong Kong.DesignA population-based prospective cohort of 65,510 Chinese enrolled from 1998 to 2001 and followed until May 2012.SettingAll 18 Elderly Health Service centres in Hong Kong, China.ParticipantsOlder people aged 65+ yearsMeasurementsSelf-reported smoking status was assessed at baseline interview and categorized as never, former and current smokers.FindingsCompared with never smokers, after adjustment for sex, age, education, social security assistance, housing type, monthly expenditure, alcohol use, depressive symptoms and health status, the hazards ratio (HR) for current smokers was 1.89 (95% confidence interval (CI) 1.81-1.98) for all participants aged 65+ years at baseline, corresponding to an attributable fraction (AF) of about 50%, which is based on AF = (HR-1)/HR. As the effect of smoking varied with age (P for age interaction <0.001), subgroup analysis by age group showed that the adjusted HR for current smokers aged 65-84 years was 1.93 (1.84-2.03), and for 85+ years was 1.29 (1.05-1.58). All the risk estimates did not vary by sex (P for sex interaction ranged 0.74-0.89).Conclusions In Hong Kong, the risk of death from smoking appears to be the same for Chinese women as it is for men. Half of all deaths in Chinese smokers aged 65 years and over and a quarter of all deaths in Chinese smokers aged 85 years and over are caused by smoking-attributable diseases.
    Article · Oct 2014 · Addiction
  • [Show abstract] [Hide abstract] ABSTRACT: Objectives In the West, self-rated health reliably predicts death, but conceptualizations of health and cause-composition of mortality may be contextually specific. Little is known as to how self-rated health predicts death in non-Western settings. Methods Multivariable Cox regression analysis was used to assess the adjusted associations of age-comparative and self-comparative self-rated health with death from all- and specific-causes using a population-based cohort of 66,820 Chinese (65 + years) enrolled from 1998 to 2001 at 18 Elderly Health Centers in Hong Kong, and followed until May 31, 2012. Results During an average of 10.9 years follow-up, 19,845 deaths occurred with 6336 from cancer. Worse age-comparative self-rated health, compared with better, was positively associated with death from all-causes (hazard ratio 1.68, 95% confidence interval 1.59, 1.77), cardiovascular disease (hazard ratio 1.83, 95% confidence interval 1.66, 2.02), stroke (hazard ratio 1.93, 95% confidence interval 1.63, 2.29), ischemic heart disease (hazard ratio 1.77, 95% confidence interval 1.51, 2.08), cancer (hazard ratio 1.17, 95% confidence interval 1.06, 1.30) and respiratory disease (hazard ratio 2.25, 95% confidence interval 2.01, 2.52), adjusted for age and sex. Self-comparative self-rated health was not associated with higher mortality. Conclusion Age-comparative self-rated health predicted death in older people from a non-Western setting although the association was less marked than in Western settings.
    Article · Jul 2014 · Preventive Medicine
  • Siu Yin Lee · Tsz Ho Lai · Ying Ying Hui · Kin Shing Chan
    [Show abstract] [Hide abstract] ABSTRACT: The selective aliphatic C(alpha)-C(beta) bond activation (CCA) of ethers by rhodium(III) porphyrin halides in the presence of KOH was achieved to give Rh-C(beta) alkyls up to 88% yield. The addition of H2O and a phase transfer agent Ph4PBr improved the homogeneity of the reaction mixture and significantly brought down the reaction temperature to 60 degrees C. At this mild temperature, the C(alpha) co-product was oxidized to the corresponding esters in up to 89% yield. KOH promotes the bond activation by transferring the hydroxyl group to rhodium porphyrin to generate the key intermediate Rh-III(ttp)OH (ttp = 5,10,15,20-tetratolylporphyrinate dianion).
    Article · Jul 2014 · Journal of Organometallic Chemistry
  • [Show abstract] [Hide abstract] ABSTRACT: In Western countries, diabetes mellitus is positively associated with death from all- and specific-causes including cancer, cardiovascular and respiratory diseases. In a Chinese setting with a different disease pattern: high diabetes rates in a relatively non-obese population with low ischemic heart disease (IHD) rates where diabetes is positively associated with IHD, we examined the association of self-reported diabetes with death among older people. Multivariable Cox regression analysis was used in a population-based prospective cohort of 66,820 Chinese (65+ years) enrolled from July 1998 to December 2001 at Elderly Health Centers of the Hong Kong Government Department of Health, followed until May 31, 2012. During 10.9years of follow-up, 19,845 deaths occurred. Self-reported diabetes was associated with death from all-causes (hazard ratio (HR)=1.56, 95% confidence interval (CI) 1.51, 1.62), cardiovascular disease (HR=1.84, 95% CI 1.72, 1.96), cancer (HR=1.11, 95% CI 1.03 to 1.20), liver cancer (HR=1.38, 95% CI 1.13 to 1.69) and stomach cancer (HR=1.38, 95% CI 1.03 to 1.85), adjusted for age, sex, socio-economic position, alcohol use, smoking, exercise and body mass index. Such a pattern of associations suggests further investigation into the drivers of diabetes is required in this and similar populations.
    Article · Apr 2014 · Preventive Medicine
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    [Show abstract] [Hide abstract] ABSTRACT: In Western settings, moderate drinking is negatively associated with respiratory disease. However, moderate drinking is socially patterned, making this association vulnerable to contextual biases. Evidence from other contexts where the typical drinking pattern is different may clarify such observations. Multivariable Cox regression analysis was used to assess the adjusted associations of alcohol use with death from respiratory disease using a population-based prospective cohort of 66,820 Chinese aged ≥65years enrolled from July 1998 to December 2001 at all the 18 Elderly Health Centers of the Hong Kong Government Department of Health and followed till May 30, 2012. During ten-year follow-up, 4065 deaths from respiratory disease occurred. Most current drinkers were occasional drinkers (<1day/week). Both moderate and occasional drinking (<1day/week) were associated with a lower risk of death from respiratory disease, but the point estimates and pattern of associations were similar between these two types of drinkers. The typical drinking pattern, i.e. occasional drinking (<1day/week), which is unlikely to have any biological effect, was similarly associated with a lower risk of respiratory disease as moderate alcohol use, suggesting the attributes of being a typical drinker may be protective.
    Full-text available · Article · Sep 2013 · Preventive Medicine
  • Siu Yin Lee · Kin Shing Chan
    [Show abstract] [Hide abstract] ABSTRACT: Photocatalytic carbon–carbon σ-bond oxidation of unstrained ketones by water using rhodium(III) porphyrin catalyst was accomplished. The catalysis yielded the corresponding one-carbon-less carbonyl compound and H2 with up to 30 turnovers in both aliphatic and cyclic ketones with α substituents. No carbon loss was observed in aromatic ketone. Mechanistic studies suggest that (Ph3P)RhIII(ttp)OH (ttp = tetratolylporphyrinato dianion) is the key intermediate in the carbon–carbon σ-bond anaerobic oxidation.
    Article · Sep 2013 · Organometallics
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    [Show abstract] [Hide abstract] ABSTRACT: In observational studies of Western populations, moderate alcohol use is usually associated with lower cancer mortality rates. However, moderate alcohol use (regular drinking of moderate amounts) is socially patterned. Evidence from other contexts can clarify such observations. We examined the association of moderate alcohol use with death from cancer in older Chinese adults from a developed non-Western setting, where occasional alcohol drinking (less than once per week of small amounts) is typical. Multivariable Cox regression analysis was used to assess the adjusted associations of alcohol use with death from cancer using a population-based prospective cohort of 66 820 Chinese aged ≥65 years enrolled from July 1998 to December 2001 at all the 18 Elderly Health Centres of the Hong Kong Government Department of Health, and followed till 30 May 2012. After follow-up for about 10.5 years, 6335 cancer deaths were identified. Most current alcohol users were social drinkers (<1/week). Moderate drinkers had a similar risk of death from non-oesophageal cancer as never drinkers, but a higher risk of oesophageal cancer, adjusted for age, sex, socioeconomic position, lifestyle and health status. Social drinking (<1/week) was associated with a lower risk of death from non-oesophageal cancer, but not from oesophageal cancer. In a non-Western setting, no association of moderate alcohol use with death from cancer was found. Occasional social drinking (<1/week) was associated with a lower risk of cancer, suggesting that moderate alcohol use is not protective, but in any setting the attributes of being a typical drinker may be.
    Full-text available · Article · Aug 2013 · Journal of epidemiology and community health
  • [Show abstract] [Hide abstract] ABSTRACT: Background and purpose: Hemorrhagic stroke is more common in non-Western settings and does not always share risk factors with other cardiovascular diseases. The association of smoking with hemorrhagic stroke subtypes has not been established. We examined the association of cigarette smoking with hemorrhagic stroke, by subtype (intracerebral hemorrhage and subarachnoid hemorrhage), in a large cohort of older Chinese from Hong Kong. Methods: Multivariable Cox regression analysis was used to assess the adjusted associations of smoking at baseline with death from hemorrhagic stroke and its subtypes, using a population-based prospective cohort of 66 820 Chinese aged>65 years enrolled from July 1998 to December 2001 at all the 18 Elderly Health Centers of the Hong Kong Government Department of Health and followed until May 31, 2012. Results: After follow-up for an average of 10.9 years (SD=3.1), 648 deaths from hemorrhagic stroke had occurred, of which 530 (82%) were intracerebral hemorrhage. Current smoking was associated with a higher risk of hemorrhagic stroke (hazard ratio, 2.19; 95% confidence interval, 1.49-3.22), intracerebral hemorrhage (1.94; 1.25-3.01), and subarachnoid hemorrhage (3.58; 1.62-7.94), adjusted for age, sex, education, public assistance, housing type, monthly expenditure, alcohol use, and exercise. Further adjustment for hypertension and body mass index slightly changed the estimates. Conclusions: Smoking is strongly associated with hemorrhagic stroke mortality, particularly for subarachnoid hemorrhage.
    Article · May 2013 · Stroke
  • Chung Sum Chan · Siu Yin Lee · Kin Shing Chan
    [Show abstract] [Hide abstract] ABSTRACT: Rhodium(III) porphyrin β-hydroxyethyl, RhIII(ttp)CH2CH2OH (ttp = 5,10,15,20-tetratolylporphyrinato dianion), was found to serve as a precursor of the highly reactive RhIII(ttp)OH for the C(CO)–C(α) bond activation (CCA) of ketones under mild and aerobic conditions of 25–50 °C.
    Article · Dec 2012 · Organometallics
  • [Show abstract] [Hide abstract] ABSTRACT: Selective aliphatic carbon(α)–carbon(β) bond activation of ethers by (5,10,15,20-tetramesitylporphyrinato)rhodium(II) (Rh(tmp) (1)) was achieved at room temperature to yield corresponding rhodium porphyrin alkyls and the functionalized esters. Rh(tmp)OH was the proposed intermediate responsible for cleaving the C(α)–C(β) bond. The reaction is general for both straight- and branch-chain ethers.
    Article · Jun 2011 · Organometallics
  • [Show abstract] [Hide abstract] ABSTRACT: Highly reactive rhodium(III) porphyrin hydroxides were formed from the ligand substitution of rhodium porphyrin halides in benzene and were rapidly reduced to rhodium(II) porphyrins and hydrogen peroxide. Thus hydroxide acted as the reducing agent. Oxidative addition of rhodium(II) porphyrin with hydrogen peroxide proceeded rapidly at room temperature to give back rhodium(III) porphyrin hydroxides. Rhodium(II) porphyrins and H2O2 therefore were thermally reversible with rhodium porphyrin hydroxides.
    Article · May 2011 · Organometallics
  • Siu Yin Lee · Chi Wai Cheung · I-Jui Hsu · Kin Shing Chan
    [Show abstract] [Hide abstract] ABSTRACT: Reaction of hydrido[5,10,15,20-tetrakis(p-tolyl)porphyrinato]iridium(III) (Ir(ttp)H) (1) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) (2) at room temperature gave a 90% yield of the unsupported iridium(II) porphyrin dimer, Ir(II)(2)(ttp)(2) (3). Kinetic measurements revealed that the oxidation followed overall second-order kinetics: rate = k[Ir(ttp)H][TEMPO], k(25 °C) = 6.65 × 10(-4) M(-1). The entropy of activation (ΔS(‡) = -25.3 ± 2.5 cal mol(-1) K(-1)) and the kinetic isotope effect of 7.2 supported a bimolecular associative mechanism in the rate-determining hydrogen atom transfer from Ir(ttp)H to TEMPO.
    Article · Oct 2010 · Inorganic Chemistry
  • Kin Shing Chan · Xin Zhu Li · Siu Yin Lee
    [Show abstract] [Hide abstract] ABSTRACT: Rh(tmp) underwent Ph(3)P-enhanced aliphatic carbon carbon bond activation with various nitroxides. (Ph(3)P)Rh(tmp), rapidly formed from Rh(tmp) and Ph(3)P, enhanced the rate, selectivity, and yield in comparison to Rh(tmp). From kinetic studies, the rate of reaction showed a first-order dependence on both Rh(tmp) and TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl) and saturation kinetics on Ph(3)P. The rate enhancement of (Ph(3)P)Rh(tmp) over Rh(tmp) was estimated to be about 11 at 70 degrees C.
    Article · Jul 2010 · Organometallics
  • Chi Wai Cheung · Hong Sang Fung · Siu Yin Lee · [...] · Kin Shing Chan
    [Show abstract] [Hide abstract] ABSTRACT: Ir(ttp)Cl(CO) (1a; ttp = 5,10,15,20-tetrakis(p-tolyl)porphyrinato dianion) was found to cleave the C−O bond of CH3OH at 200 °C to give Ir(ttp)CH3 (3a). Addition of KOH promoted the reaction rate and gave a higher yield of Ir(ttp)CH3 in 70% yield in 1 day. Mechanistic studies suggest that, in the absence of KOH, Ir(ttp)Cl(CO) reacts with CH3OH initially to give Ir(ttp)OCH3, which then undergoes β-hydride elimination to produce Ir(ttp)H (4a). Ir(ttp)H further reacts slowly to cleave the C−O bond of CH3OH, likely via σ-bond metathesis, to give Ir(ttp)CH3. In the presence of KOH, Ir(ttp)Cl(CO) initially reacts with KOH more rapidly to give Ir(ttp)OH, which then cleaves the O−H bond of CH3OH by metathesis to give Ir(ttp)OCH3. Ir(ttp)OCH3 further isomerizes via β-hydride elimination/reinsertion to give Ir(ttp)CH2OH and concurrently undergoes base-assisted β-proton elimination to give Ir(ttp)−K+ (5a). Ir(ttp)CH2OH subsequently condenses with CH3OH to form Ir(ttp)CH2OCH3 (2). Finally, Ir(ttp)−K+ cleaves the C−O bond in CH3OH, most probably via nucleophilic substitution, to give Ir(ttp)CH3. Ir(ttp)CH2OCH3 also serves as the precursor of Ir(ttp)−K+ as it undergoes nucleophilic substitution by KOH to give Ir(ttp)−K+.
    Article · Feb 2010 · Organometallics
  • [Show abstract] [Hide abstract] ABSTRACT: Rh(ttp)Cl (1a) (ttp = 5,10,15,20-tetrakistolylporphyrinato dianion) was found to react with methanol at a high temperature of 150 °C in the presence of inorganic bases to give a high yield of Rh(ttp)CH3 (2a), up to 87%. Rh(ttp)H (1d) is suggested to be the key intermediate for the carbon−oxygen bond cleavage.
    Article · Jul 2009 · Organometallics