Fe(II)-Catalyzed Imidation of Allyl Sulfides and Subsequent [2,3]-Sigmatropic Rearrangement. Preparation of α-Branched N-tert-Butyloxycarbonyl (Boc)-Protected N-Allylamines
摘要:
Allyl aryl sulfides 1 and 5 were shown to undergo an imidation/[2,3]-sigmatropic rearrangement reaction upon treatment with N-tert-butyloxycarbonyl azide (BocN(3)) and catalytic amounts of FeCl2 in CH2Cl2. The N-Boc-protected N-allyl sulfenamides 3 and 21 were obtained in yields between 48 and 75% (12 examples), Whereas the reaction is well suited for the transformation of alpha-unbranched sulfides to a-branched sulfenamides, the enantiomerically pure alpha-branched sulfides 10 and 13 reacted sluggishly. The corresponding sulfenamides 22 and 23 were obtained in only moderate enantiomeric excess (36-39% eel. A reaction mechanism is proposed that postulates the intermediacy of an N-Boc-substituted Fe(IV)-nitrene complex 14 acting as the imidation reagent in the catalytic cycle. Possible side reactions are discussed. The benzenesulfenamides 3 were further converted into N-Boc-N-allylamines 4 by removal of the phenylsulfanyl group. Bu3SnH in benzene was found to be the reagent of choice for the deprotection of alpha-branched amines that bear a secondary allyl substituent (five examples, 71-93% yield). This method failed for the alpha-branched amines 3i-k with a tertiary allyl substituent. The phenylsulfanyl group was finally removed with P(OEt)(3)/NEt3 in CH2Cl2 (three examples, 43-62% yield).
Fe(II)-Catalyzed Imidation of Allyl Sulfides and Subsequent [2,3]-Sigmatropic Rearrangement. Preparation of α-Branched N-tert-Butyloxycarbonyl (Boc)-Protected N-Allylamines
摘要:
Allyl aryl sulfides 1 and 5 were shown to undergo an imidation/[2,3]-sigmatropic rearrangement reaction upon treatment with N-tert-butyloxycarbonyl azide (BocN(3)) and catalytic amounts of FeCl2 in CH2Cl2. The N-Boc-protected N-allyl sulfenamides 3 and 21 were obtained in yields between 48 and 75% (12 examples), Whereas the reaction is well suited for the transformation of alpha-unbranched sulfides to a-branched sulfenamides, the enantiomerically pure alpha-branched sulfides 10 and 13 reacted sluggishly. The corresponding sulfenamides 22 and 23 were obtained in only moderate enantiomeric excess (36-39% eel. A reaction mechanism is proposed that postulates the intermediacy of an N-Boc-substituted Fe(IV)-nitrene complex 14 acting as the imidation reagent in the catalytic cycle. Possible side reactions are discussed. The benzenesulfenamides 3 were further converted into N-Boc-N-allylamines 4 by removal of the phenylsulfanyl group. Bu3SnH in benzene was found to be the reagent of choice for the deprotection of alpha-branched amines that bear a secondary allyl substituent (five examples, 71-93% yield). This method failed for the alpha-branched amines 3i-k with a tertiary allyl substituent. The phenylsulfanyl group was finally removed with P(OEt)(3)/NEt3 in CH2Cl2 (three examples, 43-62% yield).
Chiral (OC)Ru(salen)-catalyzed tandem sulfimidation and [2,3]sigmatropic rearrangement: asymmetric CN bond formation
作者:Masakazu Murakami、Tsutomu Katsuki
DOI:10.1016/s0040-4039(02)00603-2
日期:2002.5
manner by using (OC)Ru(salen)-catalyzed sulfimidation and the subsequent [2,3]sigmatropic rearrangement: treatment of allyl aryl sulfides with p-toluenesulfonyl azide in the presence of a catalytic amount of (OC)Ru(salen) followed by hydrolysis of the resulting N-allyl-N-arylthio toluenesulfonamides provided N-allyl toluenesulfonamides of high enantiomeric excess.
Fe(II)-Catalyzed Imidation of Allyl Sulfides and Subsequent [2,3]-Sigmatropic Rearrangement. Preparation of α-Branched <i>N</i>-<i>tert</i>-Butyloxycarbonyl (Boc)-Protected <i>N</i>-Allylamines
作者:Thorsten Bach、Christina Körber
DOI:10.1021/jo991569p
日期:2000.4.1
Allyl aryl sulfides 1 and 5 were shown to undergo an imidation/[2,3]-sigmatropic rearrangement reaction upon treatment with N-tert-butyloxycarbonyl azide (BocN(3)) and catalytic amounts of FeCl2 in CH2Cl2. The N-Boc-protected N-allyl sulfenamides 3 and 21 were obtained in yields between 48 and 75% (12 examples), Whereas the reaction is well suited for the transformation of alpha-unbranched sulfides to a-branched sulfenamides, the enantiomerically pure alpha-branched sulfides 10 and 13 reacted sluggishly. The corresponding sulfenamides 22 and 23 were obtained in only moderate enantiomeric excess (36-39% eel. A reaction mechanism is proposed that postulates the intermediacy of an N-Boc-substituted Fe(IV)-nitrene complex 14 acting as the imidation reagent in the catalytic cycle. Possible side reactions are discussed. The benzenesulfenamides 3 were further converted into N-Boc-N-allylamines 4 by removal of the phenylsulfanyl group. Bu3SnH in benzene was found to be the reagent of choice for the deprotection of alpha-branched amines that bear a secondary allyl substituent (five examples, 71-93% yield). This method failed for the alpha-branched amines 3i-k with a tertiary allyl substituent. The phenylsulfanyl group was finally removed with P(OEt)(3)/NEt3 in CH2Cl2 (three examples, 43-62% yield).