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ABSTRACT: A novel and efficient cleavage reagent, trimethyl aluminum, for traceless sulfinate-functionalized resin has been developed. The synthesis of sulfonamide and urea derivatives via a traceless solid-phase sulfone linker strategy through six synthetic steps comprising utilization of trimethyl aluminum as a novel cleavage reagent was also established. An insight of the plausible mechanism of the cleavage reaction was discussed.
Molecular Diversity 06/2012; 16(3):463-76. · 3.15 Impact Factor
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04/2002;
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ABSTRACT: The synthesis of alkyl-substituted pentaoxa[5]peristylanes has been accomplished by ozonolysis of 2,3-bis-endo-7-anti-triacylnorbornenes 6a-d and by direct chemical transformation of the tetraacetal tetraoxa cages 11 and 12. Various reaction conditions have been used to optimize the overall yield for the synthesis of methyl group substituted pentaoxa[5]peristylane 7d. Ozonolysis of 6d in CDCl(3) at -78 degrees C without reduction was performed to study the ozonolysis chemistry of the triacylnorbornenes 6a-d. The synthesis of the parent (unsubstituted) compound 25 of pentaoxa[5]peristylane has been accomplished by a three-step efficient sequence with a maximum 45% overall yield via ozonolysis of the dihemiacetal 24. The structure of pentaoxa[5]peristylanes was proven by X-ray analysis of the parent compound 25. The syntheses of the triacetal tetraoxa cage 26, a new type of oxa cage, and a new entry for the synthesis of the parent compound 33 of tetraacetal tetraoxa cages were also demonstrated.
The Journal of Organic Chemistry 04/1999; 64(5):1576-1584. · 4.45 Impact Factor
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ABSTRACT: The synthesis of diacetal trioxa-cage compounds with a new type of skeleton is reported. Ozonolysis of the diols 2a−f, 21, 24, and 33 in CH2Cl2 at −78 °C followed by reduction with Me2S gave the diacetal trioxa-cages 3a−f, 22, 25, and 34 in 70−80% yields, respectively. A mechanism via an intramolecular nucleophilic addition of the hydroxy group of the diols to the carbonyl oxide group is proposed for the formation of the diacetal trioxa-cages. The effect of the number of carbon atoms at the bridge of the diols on the formation of the diacetal trioxa-cage skeleton was examined. Ozonolysis of the diols 13 and 15 under the same reaction conditions gave compounds 16 and 18, respectively. No detectable amount of the trioxa-cages 17 and 19 was obtained. For the synthesis of the diacetal trioxa-cages 28a−c and 31, which possess an alkene bond intact, ozonolysis of the diols 27a−c and 30 was performed by controlling the amount of ozone.
10/1998;
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ABSTRACT: The synthesis of diacetal trioxa-cage compounds via a sequential cyclization reaction of norbornene derivatives induced by electrophiles in a short sequence is reported. Treatment of the norbornene derivatives 2a−d and 10b with I2 in aqueous THF in the presence of KI at 25 °C regioselectively gave the iodo-cage compounds 3a−d and 11 in 80−90% yields, respectively, via a iodine-induced sequential cyclization reaction. No detectable amount of other regioisomers or monocyclization products was obtained. The synthesis of trioxa-cages 14a−e was accomplished from 3a−d and 11 in a two-step sequence. Treatment of diacylnorbornenes 15a−f with I2 in aqueous THF at 25 °C regioselectively and stereoselectively gave the sequential cyclization products 16a−f, respectively, which were converted in one step to the diacetal trioxa-cages 24a−f in high yields. The structure of these trioxa-cages was proven by X-ray analysis of the crystalline compound 14e. Other electrophiles, such as bromine, m-CPBA, and Hg(OAc)2, were also found to be effective for the sequential cyclization reaction. Oxymercuration of 15a−f and 2a−c with Hg(OAc)2 in aqueous THF followed by reduction with NaBH4 at 25 °C gave compounds 28a−f and 30b,d,c in high yields, respectively.
09/1997;
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ABSTRACT: 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 TiCl(4) 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 TiCl(4) 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 TiCl(4) or MeSO(3)H 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.
The Journal of Organic Chemistry 06/1997; 62(10):3208-3214. · 4.45 Impact Factor
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ABSTRACT: 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 CDCl(3) 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, 11, and 12 was obtained. A mechanism is proposed to account for the exclusive regioselective fragmentation of the primary ozonides. Ozonolysis of 3a-d, 8a, and 8b in CH(2)Cl(2) 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 CH(2)Cl(2) 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 CDCl(3) 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 CH(2)Cl(2) 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.
The Journal of Organic Chemistry 06/1996; 61(11):3820-3828. · 4.45 Impact Factor
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Tetrahedron. 53(52):17653-17668.
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Tetrahedron Letters 38(16):2887-2890. · 2.68 Impact Factor
