Browsing by Author "Wu, HJ"

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A novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids
(1997-03-21)
Wu, HJ
;
Chern, JH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
Treatment of tetraoxa-cages 1a-f with Lewis acids such as TlC4, AlCl3, BF3 . OEt(2) and MeSO(3)H in dichloromethane at 25 degrees C gives the rearrangement products 2a-f in 90% yields regioselectively and stereoselectively; a novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids.
A novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids
(1997-03-21)
Wu, HJ
;
Chern, JH
;
應用化學系
;
Department of Applied Chemistry
Treatment of tetraoxa-cages 1a-f with Lewis acids such as TlC4, AlCl3, BF3 . OEt(2) and MeSO(3)H in dichloromethane at 25 degrees C gives the rearrangement products 2a-f in 90% yields regioselectively and stereoselectively; a novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids.
A novel iodine-induced sequential cyclization reaction of norbornene derivatives leading to the formation of novel iodo-cage compounds
(1996-02-07)
Wu, HJ
;
Tsai, SH
;
Chung, WS
;
交大名義發表
;
應用化學系
Treatment of the bis-endo-thioester and acyl group substituted norbornenes 1a-d and 9a-c with iodine in aqueous tetrahydrofuran at 25 degrees C gave the novel iodo-cage compounds 2a-d and 10a-c in 80-90% yields respectively, the first example of sequential cyclization of norbornene derivatives induced by an iodine electrophile.
A novel one-pot conversion of tetraacetal tetraoxa-cages to aza-cages mediated by iodotrimethylsilane in acetonitrile
(1997-04-21)
Wu, HJ
;
Chern, JH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
Treatment of the tetraacetal tetraoxa-cages 1a-f with excess of iodotrimethylsilane in acetonitrile at 25 degrees C gave the novel tetraacetal trioxamonoaza-cages 2a-f in 75-80% yields respectively, a novel one-pot conversion of era-cages to ata-cages. (C) 1997 Elsevier Science Ltd.
A novel one-pot conversion of tetraacetal tetraoxa-cages to aza-cages mediated by iodotrimethylsilane in acetonitrile
(1997-04-21)
Wu, HJ
;
Chern, JH
;
應用化學系
;
Department of Applied Chemistry
Treatment of the tetraacetal tetraoxa-cages 1a-f with excess of iodotrimethylsilane in acetonitrile at 25 degrees C gave the novel tetraacetal trioxamonoaza-cages 2a-f in 75-80% yields respectively, a novel one-pot conversion of era-cages to ata-cages. (C) 1997 Elsevier Science Ltd.
A remarkable effect of C-O-C bond angle strain on the regioselective double nucleophilic substitution of the acetal group of tetraacetal tetraoxa-cages and a novel hydride rearrangement of tetraoxa-cages
(1997-05-16)
Wu, HJ
;
Chern, JH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
A remarkable effect of C-O-C bond angle strain on the regioselective double nucleophilic substitution of the acetal group of tetraacetal tetraoxa-cages and a novel regioselective and stereoselective hydride rearrangement of tetraoxa-cages are reported. Reaction of the tetraacetal tetraoxa-cages 1 with 3 equiv of triethylsilane (at -78 degrees C), cyanotrimethylsilane (at 25 degrees C), and allyltrimethylsilane (at -78 degrees C) in dichloromethane in the presence of TiCl4 gave the double nucleophilic substitution products 2, 6, and 7 in 85-90% yields, respectively. No detectable amount of other regioisomers was obtained. Reaction of 1a with (methylthio)trimethylsilane and (phenylthio)trimethylsilane in dichloromethane in the presence of TiCl4 at -78 degrees C gave the symmetric products 10a,b and the unsymmetric products 11a,b in ratios of 8-10:1. The stereochemistry of the symmetric substitution products was proven by X-ray analysis of the crystalline compound 10a. The mechanism of the double nucleophilic substitution of the tetraoxa-cages 1 are discussed. Treatment of the tetraoxa-cages 1a,c and 22a-c with 2 equiv of TiCl4 or MeSO3H in dichloromethane at 25 degrees C for 3 h regioselectively and stereoselectively gave the novel hydride rearrangement products 16a,b and 23a-c respectively. No detectable amount of other regioisomers was observed. The stereochemistry of the hydride rearrangement was proven by DIBAL-H reduction of 16 and 23 and X-ray analysis of the reduction product 24a. We attribute the high regioselectivity of the double nucleophilic substitution and the hydride rearrangement of the tetraoxa-cages 1 to the bond angle strain of the unusually large bond angle of C(3)-O(4)-C(5) of the tetraoxa-cages.
Chemical transformation of tetraacetal tetraoxa-cages to aza-cages and amido-cages mediated by iodotrimethylsilane and the combination of chlorotrimethylsilane and sodium iodide in nitriles
(1998-05-28)
Chern, JH
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Wu, HJ
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應用化學系
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Department of Applied Chemistry
An one-pot conversion of tetraacetal tetraoxa-cages la-e to aza-cages 2a-e mediated by iodotrimethylsilane in alkyl nitriles at 25 degrees C via the ring expansion compound 9 as the reaction intermediate was discovered. A Ritter-type reaction was proposed for the mechanism of this conversion. On the other hand, reaction of tetraacetal tetraoxa-cages 1 with Me3SiCl and NaI in nitriles at 25 degrees C gave the amido-cages 12. Conjugated nitriles and Lewis acids, such as TiCl4 or BF3 . OEt2 were found to be ineffective for the conversion of era-cages to aza-cages. The structures of 2a and chemical transformation product 16 were proven by X-ray analysis. (C) 1998 Elsevier Science Ltd. All rights reserved.
Chemical transformations of 4,6-dimethyl-2 beta-hydroxy-8-oxo-3,5,7-trioxatetracyclo[7.2.1.0(4,11).0(6,10)]dodecane
(1997-02-01)
Chem, JH
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Wu, HJ
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
Reactions of 4,6-dimethyl-2 beta-hydroxy-8-oxo-3,5,7-trioxatetracyclo-[7.2.1.0(4,11).0(6,10)] dodecane 1 with nucleophiles have been studied. Reaction of 1 with alcohols, triethylsilane, allyltrimethylsilane,and methylthiotrirnethylsilane in CH2Cl2 in the presence of TiCl4 gave the substitution products 2, 7a, 7b, and 7c in 80-90% yields. The substitution reaction took place chemoselectively on the hemiacetal group of 1. Reaction of 1 with cyanotrimethylsilane in CH2Cl2 in the presence of TiCl4 gave compound 8 and the rearranged product 9. The structure of 9 was proven by X-ray analysis.
Chemical transformations of 4,6-dimethyl-2 beta-hydroxy-8-oxo-3,5,7-trioxatetracyclo[7.2.1.0(4,11).0(6,10)]dodecane
(1997-02-01)
Chem, JH
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
Reactions of 4,6-dimethyl-2 beta-hydroxy-8-oxo-3,5,7-trioxatetracyclo-[7.2.1.0(4,11).0(6,10)] dodecane 1 with nucleophiles have been studied. Reaction of 1 with alcohols, triethylsilane, allyltrimethylsilane,and methylthiotrirnethylsilane in CH2Cl2 in the presence of TiCl4 gave the substitution products 2, 7a, 7b, and 7c in 80-90% yields. The substitution reaction took place chemoselectively on the hemiacetal group of 1. Reaction of 1 with cyanotrimethylsilane in CH2Cl2 in the presence of TiCl4 gave compound 8 and the rearranged product 9. The structure of 9 was proven by X-ray analysis.
First exclusive regioselective fragmentation of primary ozonides controlled by remote carbonyl groups and a new method for determining the regiochemistry of carbonyl oxide formation
(1996-05-31)
Wu, HJ
;
Lin, CC
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交大名義發表
;
應用化學系
;
National Chiao Tung University
The first exclusive regioselective fragmentation of primary ozonides controlled by remote carbonyl groups on ozonolysis of norbornene derivatives and reaction of final ozonides with triethylamine as a new probe for determining the regiochemistry of carbonyl oxide formation from primary ozonide fragmentation are reported. Ozonolysis of the endo adducts 3a-d and the deuterated compounds 8a and 8b in CDCl3 at -78 degrees C gave the final ozonides 4a-d, 9a, and 9b as the sole products (>95%), respectively. No detectable amount of the isomeric final ozonides 5, 10, ii, and 12 was obtained. A mechanism is proposed to account for the exclusive regioselective fragmentation of the primary ozonides. Ozonolysis of 3a-d, Ba, and 8b in CH2Cl2 at -78 degrees C followed by treatment with triethylamine exclusively gave the convex tetraquinane oxa cage compounds 16a-d, 19a, and 19b in 85-90% yields, respectively. No detectable amount of the other regioisomers 17a-d, 20a, and 20b was obtained. Ozonolysis of 3a-d, 8a, and 8b in CH2Cl2 at -78 degrees C followed by reduction with dimethyl sulfide gave the tetraacetal tetraoxa cage compounds 21a-d, 23a, and 23b in 85% yields, respectively. The difference in function between triethylamine and dimethyl sulfide in reaction with final ozonide is demonstrated. Ozonolysis of the endo adducts 24a and 24b in CDCl3 at -78 degrees C exclusively gave the final ozonides 27a and 27b, respectively, The order of the preference of various remote carbonyl groups to control the fragmentation of the primary ozonides formed by ozonolysis of norbornene derivatives is investigated. Ozonolysis of the endo esters 32a-c in CH2Cl2 at -78 degrees C followed by reduction with dimethyl sulfide gave the new tetraacetal oxa cages 35a-c, with an alkoxyl group directly on the skeleton, and the novel triacetal oxa cages 36b and 36c, respectively. The structures of triacetal oxa cages are proven for the first time by X-ray analysis of the crystalline compound 36c.
Intramolecular Diels-Alder reaction of furans with allenyl ethers followed by phenylthio and trialkylsilyl groups rearrangement
(1998-12-01)
Chuang, CT
;
Yen, CH
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
a new reaction involving an intramolecular Diels-Alder reaction of a furan diene with an allenyl ether dienophile followed by phenylthio group rearrangement was discovered. Treatment of the propargyl ethers 2a-c with t-BuOK in t-BuOH at 85 degrees C gave the phenylthio group rearrangement products 5a-c and 6a-c. A reaction involving an intramolecular Diels-Alder reaction of a furan diene with an allenyl ether dienophile followed by trialkylsilyl group rearrangement is also demonstrated.
Intramolecular Diels-Alder reaction of furans with allenyl ethers followed by phenylthio and trialkylsilyl groups rearrangement
(1998-12-01)
Chuang, CT
;
Yen, CH
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
a new reaction involving an intramolecular Diels-Alder reaction of a furan diene with an allenyl ether dienophile followed by phenylthio group rearrangement was discovered. Treatment of the propargyl ethers 2a-c with t-BuOK in t-BuOH at 85 degrees C gave the phenylthio group rearrangement products 5a-c and 6a-c. A reaction involving an intramolecular Diels-Alder reaction of a furan diene with an allenyl ether dienophile followed by trialkylsilyl group rearrangement is also demonstrated.
Intramolecular Diels-Alder reaction of furans with allenyl ethers followed by sulfur and silicon atom-containing group rearrangement
(1998-07-24)
Wu, HJ
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Yen, CH
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Chuang, CT
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應用化學系
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Department of Applied Chemistry
The intramolecular Diels-Alder reactions of a furandiene with an allenyl ether dienophile followed by the alkylthio, alkylsulfinyl, alkylsulfonyl, and trimethylsilyl group rearrangements are reported. Refluxing the propargyl ether 3 with t-BuOK in t-BuOH at 85 degrees C gave the 1,4-rearrangement product 4 exclusively. The alkylthio group 1,4-rearrangement may proceed intramolecularly via the tight; ion pairs. Refluxing the 5-(alkylsulfinyl)-2-furfuryl propargyl ethers 9a-e and the 5-(alkylsulfonyl)-2-furfuryl propargyl ethers 19a-e under the same reaction conditions gave the alkylsulfinyl group and the alkylsulfonyl group 1,2-rearrangement products 10a-e and 20a-e, respectively. No detectable amount of the corresponding 1,4-rearrangement products 11a-e and 21a-e was obtained. In the cases of 9b and 19b, which possess two furfurylic hydrogen atoms, no detectable amount of the furan ring-transfer reaction products was obtained. Refluxing the 5-(trimethylsilyl)-2-furfuryl propargyl ethers 25a-d with t-BuOK in t-BuOH at 85 degrees C for 10 h gave the trimethylsilyl group 1,2-rearrangement products 26a-d and Brook rearrangement products 27a-d. The reaction mechanisms for these novel intramolecular Diels-Alder reactions are discussed. In the case of 37, which possesses two furfurylic hydrogen atoms, compound 38 was obtained via an intramolecular Diels-Alder reaction followed by the furan ring-transfer reaction and Brook rearrangement.
Intramolecular Diels-Alder reaction of furans with allenyl ethers followed by trimethylsilyl group 1,2-rearrangement and Brook rearrangement
(1996-10-07)
Wu, HJ
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Yen, CH
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Chuang, CT
;
應用化學系
;
Department of Applied Chemistry
The base-catalyzed intramolecular Diels-Alder reactions of 5-trimethylsilyl-2-furfuryl propargyl ethers la-lf gave compounds 2a-2f and 3a-3f in 70-90% yields respectively, a novel reaction involving an intramolecular Diels-Alder reaction followed by a trimethylsilyl group 1,2-rearrangement and Brook rearrangement. Copyright (C) 1996 Elsevier Science Ltd
Intramolecular Diels-Alder reaction of furans with allenyl ethers followed by trimethylsilyl group 1,2-rearrangement and Brook rearrangement
(1996-10-07)
Wu, HJ
;
Yen, CH
;
Chuang, CT
;
交大名義發表
;
應用化學系
The base-catalyzed intramolecular Diels-Alder reactions of 5-trimethylsilyl-2-furfuryl propargyl ethers la-lf gave compounds 2a-2f and 3a-3f in 70-90% yields respectively, a novel reaction involving an intramolecular Diels-Alder reaction followed by a trimethylsilyl group 1,2-rearrangement and Brook rearrangement. Copyright (C) 1996 Elsevier Science Ltd
Iodine-induced cyclization reaction of endo-thioester substituted norbornenes followed by methylthio group rearrangement
(1996-11-04)
Wu, HJ
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Tsai, SH
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Chung, WS
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應用化學系
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Department of Applied Chemistry
Treatment of the endo-thioester group substituted norbornenes 3a-3d with iodine in aqueous tetrahydrofuran at 25 degrees C gave the novel methylthio group rearranged lactonization products 4a-4d in 80% yields; iodolactonization reaction of 9 was applied to the synthesis of novel diacetal trioxa-cage compound 13. Copyright (C) 1996 Elsevier Science Ltd
New insight into the degradation mechanism of nitride spacer with different post-oxide in submicron LDD n-MOSFET's
(1998-03-01)
Yih, CM
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Wang, CL
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Chung, SS
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Wu, CC
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Tan, W
In this paper, the hot carrier degradation mechanisms in lightly-doped drain (LDD) n-MOS devices with silicon nitride spacer have been investigated. A low temperature chemical vapor deposited (CVD) SiO2 oxide is used as a post-oxide between source/drain surface and the nitride spacer. The gated-diode measurement in combination with the gate-induced drain leakage (GIDL) current measurement techniques have been used to analyze the stress-induced interface state and oxide charges. For the first time, it was found that the oxide charge but not the interface state generation in the post oxide will dominate the device drain current degradation. Moreover, the CVD post oxide with N-2 annealing has been proposed which is able to effectively suppress the generation of oxide charges and significantly improve the device hot carrier reliability. The scaling of gate oxide thickness and the optimization of source/drain junction to improve the device reliability are also demonstrated.
Ozonolysis of 2-endo-7-anti-diacylnorbornenes. A new entry for the synthesis of 2,4,6,13-tetraoxapentacyclo[5.5.1.0(3,11).0(5,9).0(8,12)]tridecanes
(1997-02-17)
Wu, HJ
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Chern, JH
;
Wu, CY
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交大名義發表
;
應用化學系
A new route for the synthesis of the title compounds 4a, 4b, 10a, and 10b has been developed via ozonolysis of 2-endo-7-anti-diacylnorbornenes 3a, 3b, 9a, and 9b. The synthesis of the unsubstituted (parent) compound 4a of tetraacetal tetraoxa-cages has been accomplished for the first time by this new entry. Ozonolysis reactions of 3a, 3b, and 9a were also performed in CDCl3 for understanding the final ozonide structures and the ozonation chemistry. Ozonolysis of 3a, 3b, and 9a in CH2Cl2 at -78 degrees C followed by treatment with triethylamine provided an indirect support for the structures of the final ozonides 11a, 11b, and 14. (C) 1997, Elsevier Science Ltd.
Quantum mechanical study on the facial selectivity of dioxa and trioxa cage molecules
(2000-11-03)
Chao, I
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Shih, JH
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Wu, HJ
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應用化學系
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Department of Applied Chemistry
High facial selectivity (> 99%) of nucleophilic addition to the carbonyl groups of the title compounds (1 and 2) has been achieved for the novel trioxa cage 2, but not for the dioxa 1. Similar experimental observations were made for the carbene addition to the double bonds of cage compounds, 3 and 4. Calculations were carried out for the cage compounds and their reaction transition structures, with LiH as a nucleophile and :CCl2 as an attacking carbene. The calculated facial preference for nucleophilic and carbene addition agreed well with experimental results. The origins of facial selectivity are examined from the viewpoints of structure, frontier orbitals, and molecular electrostatic potential of the reactants, as well as strain, electrostatic, and hyperconjugation effects in the transition state;For dioxa cages; the structural facial difference around the reaction center is minor, but the electronic difference of syn and anti faces generated by the two remote oxygen atoms is clearly demonstrated via frontier orbital and MEP analyses. For trioxa cages, the close proximity of the third ether oxygen (O-s) to the reaction center brings large structural and electronic changes around the reaction center. The calculated electrostatic and strain energy differences of syn and anti transition structures are significantly larger for trioxa cages than for the dioxa cages. Therefore, they both contribute to the enhanced facial selectivity of trioxa compounds. Finally, analysis of hyperconjugative stabilization in transition structures reveals the danger of relying solely on Cieplak or Anh models in rationalization of facial selectivity, especially when nonequivalent steric and electrostatic effects as those present in the trioxa systems are involved.
Stereoselectivity of the Diels-Alder reaction of (E)gamma-Oxo-alpha,beta-unsaturated thioesters with cyclopentadiene
(1996-06-01)
Tsai, SH
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Chung, WS
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Wu, HJ
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應用化學系
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Department of Applied Chemistry
The stereoselectivity of the Diels-Alder reaction of (E)-gamma-oxo-alpha,beta-unsaturated thioesters 3a-3d with cyclopentadiene is greatly enhanced in the presence of Lewis acids favoring the endo acyl isomers 4a-4d. In the absence of Lewis acid, Diels-Alder reaction of 3a-3d with cyclopentadiene at 25 degrees C gave two adducts 4a-4d and 5a-5d in a ratio of 1:1 respectively. In the presence of Lewis acids, Diels-Alder reaction of 3a-3d with cyclopentadiene gave 4a-4d and 5a-5d in ratios of 75 similar to 94:25 similar to 6 respectively. The stereoelectivity was enhanced to ratios of 95 similar to 98:5 similar to 2 with lowering the reaction temperature. The stereochemistry of the cycloadducts 4 and 5 was confirmed by iodocyclization. Reaction of the endo-thioester 5c with I-2 in aqueous THF at 0 degrees C gave the novel methylthio group rearranged product 6c in 80% yield, the first example of iodolactonization of endo-thioesters. Reaction of the endo-acyl isomer 4b with I-2 under the same reaction conditions gave an isomeric mixture of 7b and 8b in 1:2 ratio. The stereochemistry of the thioester group in 8b was proved by X-ray single-crystal analysis. The solvent effect on the endo selectivity of (Z)-gamma-oxo-alpha,beta-unsaturated thioester 2b was also examined.