rac-2,2 0 -Diamino-3,3 0 -diethoxycarbonyl-8,8 0 -diphenyl-1,1 0 -biazulene was synthesized from diethyl 2-aminoazulene-1,3-dicarboxylate and was optically resolved into two enantiomers of S-form and R-form. The enantioselective oxidative couplings with two chiral amines [(2)-sparteine and (R)-(þ)-a-methylbenzylamine] and ferric chloride catalyst, and the asymmetric couplings with two chiral oxovanadium(IV) complexes of ethyl 2-amino-4-phenylazulene-1-carboxylate, easily yielded chiral 2,2 0 -diamino-3,3 0 -diethoxycarbonyl-8,8 0 -diphenyl-1,1 0 -biazulene. Therefore, the introduction of two phenyl groups at the 8-and 8 0 -postions of each azulene ring using phenyl magnesium bromide via an addition-oxidation-decarboxylation mechanism resulted in 1,1 0 -biazulene forming a chiral C 2 axis.
3-(Phenylsulfonyl)isoxazolines, readily obtained from alkenes by cycloaddition with benzenesulfonylcarbonitrile oxide, undergo a variety of substitution reactions. Alkyl, aryl, and acetylenic lithium reagents, cyanide, lithium or sodium alkoxides, and sodium borohydride are all useful nucleophiles. Tandem alkylations are possible with alkyllithium reagents when excess base and alkyl iodide are used. Excess base can also be used to cleave the isoxazoline ring of the initial substitution products. 3-(2-Propenyloxy)isoxazolines will undergo an aza-Claisen rearrangement on heating.
Nucleophilic substitution reactions of diethyl 2‐chloroazulene‐1,3‐dicarboxylate with four alkyl lithiums (methyl lithium, ethyl lithium, n‐propyl lithium and n‐butyl lithium) afforded the major product of ethyl 2‐chloro‐4‐alkylazulene‐1‐carboxylate and some minor products of 2‐chloro‐4‐alkylazulene, 2,4‐dialkylazulene‐1‐carboxylic acid, ethyl 3,4‐dialkylazulene‐1‐carboxylate, diethyl 6‐alkylazulene‐1,3‐dicarboxylate and diethyl 2‐chloro‐5‐alkylazulene‐1,3‐dicarboxylate, respectively. The kinds and the yields of their products were significantly dependent on the kinds of alkyl lithiums, molar ratios of alkyl lithium/substrate and oxidation conditions at room temperature or under reflux. The major product of ethyl 2‐chloro‐4‐alkylazulene‐1‐carboxylate is proposed to be formed via an addition‐elimination mechanism.
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