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John P. Wolfe - One of the best experts on this subject based on the ideXlab platform.
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New Cationic Olefin Cyclization−Pinacol Reactions. Ring-Expanding Cyclopentane Annulations That Directly Install Useful Functionality in the Cyclopentane Ring
Journal of Organic Chemistry, 2002Co-Authors: Larry E. Overman, John P. WolfeAbstract:Two new tandem cationic olefin cyclization−pinacol reactions that provide cyclopentane-fused cycloalkanone products are described. Treatment of cis-1-[2-alkenyl-2-(triethylsiloxy)cycloalkyl]but-3-en-2-ol derivatives 21−24 with triflic anhydride at −78 °C affords cycloalkanones 31−34 in 54−90% yields with diastereoselectivities of typically >20:1. In this unusual transformation, the starting cycloalkanone is ring-expanded and fused to a 2-alkenylcyclopentane fragment. Reaction of cis-(2-siloxy-2-alkenylcycloalkyl)pyrrolidin-1-ylethanones 15−17 with triflic anhydride and 2,6-di-tert-butyl-4-methylpyridine (DTBMP) at −20 to +65 °C followed by hydrolysis of the intermediate iminium salts 64 with aqueous KHCO3 affords cycloalkanediones 46−48 in moderate yield and high diastereoselectivity (>20:1). These are the first examples of ring-expanding cyclopentane annulations that directly introduce a carbon side chain or carbonyl functionality at the cyclopentane C2 position. The high diastereoselectivities observed ...
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new cationic olefin cyclization pinacol reactions ring expanding cyclopentane annulations that directly install useful functionality in the cyclopentane ring
Journal of Organic Chemistry, 2002Co-Authors: Larry E. Overman, John P. WolfeAbstract:Two new tandem cationic olefin cyclization−pinacol reactions that provide cyclopentane-fused cycloalkanone products are described. Treatment of cis-1-[2-alkenyl-2-(triethylsiloxy)cycloalkyl]but-3-en-2-ol derivatives 21−24 with triflic anhydride at −78 °C affords cycloalkanones 31−34 in 54−90% yields with diastereoselectivities of typically >20:1. In this unusual transformation, the starting cycloalkanone is ring-expanded and fused to a 2-alkenylcyclopentane fragment. Reaction of cis-(2-siloxy-2-alkenylcycloalkyl)pyrrolidin-1-ylethanones 15−17 with triflic anhydride and 2,6-di-tert-butyl-4-methylpyridine (DTBMP) at −20 to +65 °C followed by hydrolysis of the intermediate iminium salts 64 with aqueous KHCO3 affords cycloalkanediones 46−48 in moderate yield and high diastereoselectivity (>20:1). These are the first examples of ring-expanding cyclopentane annulations that directly introduce a carbon side chain or carbonyl functionality at the cyclopentane C2 position. The high diastereoselectivities observed ...
Larry E. Overman - One of the best experts on this subject based on the ideXlab platform.
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New Cationic Olefin Cyclization−Pinacol Reactions. Ring-Expanding Cyclopentane Annulations That Directly Install Useful Functionality in the Cyclopentane Ring
Journal of Organic Chemistry, 2002Co-Authors: Larry E. Overman, John P. WolfeAbstract:Two new tandem cationic olefin cyclization−pinacol reactions that provide cyclopentane-fused cycloalkanone products are described. Treatment of cis-1-[2-alkenyl-2-(triethylsiloxy)cycloalkyl]but-3-en-2-ol derivatives 21−24 with triflic anhydride at −78 °C affords cycloalkanones 31−34 in 54−90% yields with diastereoselectivities of typically >20:1. In this unusual transformation, the starting cycloalkanone is ring-expanded and fused to a 2-alkenylcyclopentane fragment. Reaction of cis-(2-siloxy-2-alkenylcycloalkyl)pyrrolidin-1-ylethanones 15−17 with triflic anhydride and 2,6-di-tert-butyl-4-methylpyridine (DTBMP) at −20 to +65 °C followed by hydrolysis of the intermediate iminium salts 64 with aqueous KHCO3 affords cycloalkanediones 46−48 in moderate yield and high diastereoselectivity (>20:1). These are the first examples of ring-expanding cyclopentane annulations that directly introduce a carbon side chain or carbonyl functionality at the cyclopentane C2 position. The high diastereoselectivities observed ...
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new cationic olefin cyclization pinacol reactions ring expanding cyclopentane annulations that directly install useful functionality in the cyclopentane ring
Journal of Organic Chemistry, 2002Co-Authors: Larry E. Overman, John P. WolfeAbstract:Two new tandem cationic olefin cyclization−pinacol reactions that provide cyclopentane-fused cycloalkanone products are described. Treatment of cis-1-[2-alkenyl-2-(triethylsiloxy)cycloalkyl]but-3-en-2-ol derivatives 21−24 with triflic anhydride at −78 °C affords cycloalkanones 31−34 in 54−90% yields with diastereoselectivities of typically >20:1. In this unusual transformation, the starting cycloalkanone is ring-expanded and fused to a 2-alkenylcyclopentane fragment. Reaction of cis-(2-siloxy-2-alkenylcycloalkyl)pyrrolidin-1-ylethanones 15−17 with triflic anhydride and 2,6-di-tert-butyl-4-methylpyridine (DTBMP) at −20 to +65 °C followed by hydrolysis of the intermediate iminium salts 64 with aqueous KHCO3 affords cycloalkanediones 46−48 in moderate yield and high diastereoselectivity (>20:1). These are the first examples of ring-expanding cyclopentane annulations that directly introduce a carbon side chain or carbonyl functionality at the cyclopentane C2 position. The high diastereoselectivities observed ...
David A. Wise - One of the best experts on this subject based on the ideXlab platform.
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Does Retiree Health Insurance Encourage Early Retirement
Journal of public economics, 2013Co-Authors: Steven Nyce, Sita Nataraj Slavov, John B. Shoven, Sylvester J. Schieber, David A. WiseAbstract:The strong link between health insurance and employment in the United States may cause workers to delay retirement until they become eligible for Medicare at age 65. However, some employers extend health insurance benefits to their retirees, and individuals who are eligible for such retiree health benefits need not wait until age 65 to retire with group health coverage. We investigate the impact of retiree health insurance on early retirement using employee-level data from 54 diverse firms that are clients of Towers Watson, a leading benefits consulting firm. We find that retiree health coverage has its strongest effects at ages 62 through 64. Coverage that includes an employer contribution is associated with a 6.3 percentage point (36.2 percent) increase in the probability of turnover at age 62, a 7.7 percentage point (48.8 percent) increase in the probability of turnover at age 63, and a 5.5 percentage point (38.0 percent) increase in the probability of turnover at age 64. Conditional on working at age 57, such coverage reduces the expected retirement age by almost three months and reduces the total number of person-years worked between ages 58 and 64 by 5.6 percent.
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Does Retiree Health Insurance Encourage Early Retirement
National Bureau of Economic Research, 2011Co-Authors: Steven Nyce, Sita Nataraj Slavov, John B. Shoven, Sylvester J. Schieber, David A. WiseAbstract:The strong link between health insurance and employment in the United States may cause workers to delay retirement until they become eligible for Medicare at age 65. However, some employers extend health insurance benefits to their retirees, and individuals who are eligible for such retiree health benefits need not wait until age 65 to retire with group health coverage. We investigate the impact of retiree health insurance on early retirement using employee-level data from 64 diverse firms that are clients of Towers Watson, a leading benefits consulting firm. We find that retiree health coverage has its strongest effects at ages 62 and 63, resulting in a 3.7 percentage point (21.2 percent) increase in the probability of turnover at age 62 and a 5.1 percentage point (32.2 percent) increase in the probability of turnover at age 63; it has a more modest effects for individuals under the age of 62. A more generous employer contribution of 50 percent or more raises turnover by 1-3 percentage points at ages 56-61, by 5.9 percentage points (33.7 percent) at age 62, and by 6.9 percentage points (43.7 percent) at age 63. Overall, an employer contribution of 50 percent or more reduces the total number of person-years worked between ages 56 and 64 by 9.6 percent relative to no coverage.
Steven Nyce - One of the best experts on this subject based on the ideXlab platform.
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Does Retiree Health Insurance Encourage Early Retirement
Journal of public economics, 2013Co-Authors: Steven Nyce, Sita Nataraj Slavov, John B. Shoven, Sylvester J. Schieber, David A. WiseAbstract:The strong link between health insurance and employment in the United States may cause workers to delay retirement until they become eligible for Medicare at age 65. However, some employers extend health insurance benefits to their retirees, and individuals who are eligible for such retiree health benefits need not wait until age 65 to retire with group health coverage. We investigate the impact of retiree health insurance on early retirement using employee-level data from 54 diverse firms that are clients of Towers Watson, a leading benefits consulting firm. We find that retiree health coverage has its strongest effects at ages 62 through 64. Coverage that includes an employer contribution is associated with a 6.3 percentage point (36.2 percent) increase in the probability of turnover at age 62, a 7.7 percentage point (48.8 percent) increase in the probability of turnover at age 63, and a 5.5 percentage point (38.0 percent) increase in the probability of turnover at age 64. Conditional on working at age 57, such coverage reduces the expected retirement age by almost three months and reduces the total number of person-years worked between ages 58 and 64 by 5.6 percent.
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Does Retiree Health Insurance Encourage Early Retirement
National Bureau of Economic Research, 2011Co-Authors: Steven Nyce, Sita Nataraj Slavov, John B. Shoven, Sylvester J. Schieber, David A. WiseAbstract:The strong link between health insurance and employment in the United States may cause workers to delay retirement until they become eligible for Medicare at age 65. However, some employers extend health insurance benefits to their retirees, and individuals who are eligible for such retiree health benefits need not wait until age 65 to retire with group health coverage. We investigate the impact of retiree health insurance on early retirement using employee-level data from 64 diverse firms that are clients of Towers Watson, a leading benefits consulting firm. We find that retiree health coverage has its strongest effects at ages 62 and 63, resulting in a 3.7 percentage point (21.2 percent) increase in the probability of turnover at age 62 and a 5.1 percentage point (32.2 percent) increase in the probability of turnover at age 63; it has a more modest effects for individuals under the age of 62. A more generous employer contribution of 50 percent or more raises turnover by 1-3 percentage points at ages 56-61, by 5.9 percentage points (33.7 percent) at age 62, and by 6.9 percentage points (43.7 percent) at age 63. Overall, an employer contribution of 50 percent or more reduces the total number of person-years worked between ages 56 and 64 by 9.6 percent relative to no coverage.
Yukari N Takayabu - One of the best experts on this subject based on the ideXlab platform.
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a statistical study on rain characteristics of tropical cyclones using trmm satellite data
Monthly Weather Review, 2008Co-Authors: Chie Yokoyama, Yukari N TakayabuAbstract:Abstract Three-dimensional rain characteristics of tropical cyclones (TCs) are statistically quantified, using Tropical Rainfall Measuring Mission (TRMM) data from December 1997 to December 2003. Tropical cyclones are classified into four maximum intensity classes (<34, 34–64, 64–128, and ≥128 kt) and three stages (developing, mature, and decaying). First, rain characteristics of TCs are compared with those of the equatorial (10°N–10°S) mean. A notable finding here is that the average stratiform rain ratio (SRR), which is the contribution from stratiform rain in the total rainfall, of TCs is 52%, while it is 44% for the equatorial oceanic mean and 46% for the Madden–Julian oscillation in its mature phase. Stronger rain is observed in TCs both for convective and stratiform rain. Second, radial rain characteristics of TCs suggest that the region 0–60 km can be classified as “the inner core,” and 60–500 km as “the rainband.” The inner core is characterized with small SRR, very high rain-top height, and a lar...
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A Statistical Study on Rain Characteristics of Tropical Cyclones Using TRMM Satellite Data
Monthly Weather Review, 2008Co-Authors: Chie Yokoyama, Yukari N TakayabuAbstract:Three-dimensional rain characteristics of tropical cyclones (TCs) are statistically quantified, using Tropical Rainfall Measuring Mission (TRMM) data from December 1997 to December 2003. Tropical cyclones are classified into four maximum intensity classes (<34, 34–64, 64–128, and ≥128 kt) and three stages (developing, mature, and decaying). First, rain characteristics of TCs are compared with those of the equatorial (10°N–10°S) mean. A notable finding here is that the average stratiform rain ratio (SRR), which is the contribution from stratiform rain in the total rainfall, of TCs is 52%, while it is 44% for the equatorial oceanic mean and 46% for the Madden–Julian oscillation in its mature phase. Stronger rain is observed in TCs both for convective and stratiform rain. Second, radial rain characteristics of TCs suggest that the region 0–60 km can be classified as “the inner core,” and 60–500 km as “the rainband.” The inner core is characterized with small SRR, very high rain-top height, and a large flash rate, indicating the vigor of convective activity. In contrast, the rainband is characterized with large SRR and relatively large rain yield per flash, indicating a large rainfall amount with a moderate convective activity. An important implication of this study is that TCs are listed in the high end of tropical oceanic organized rain systems, in terms of the organization levels of rain. Last, we use the above composite results to calculate the rainfall contribution of TCs to total annual rainfall between 35°N and 35°S as 3.3% ± 0.1%.
