A Versatile and Highly Selective Hypervalent Iodine (III)/2,2,6,6-Tetramethyl-1-piperidinyloxyl-Mediated Oxidation of Alcohols to Carbonyl Compounds
摘要:
Catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) are used in combination with [bis(acetoxy)iodo]benzene (BAIB) as a stoichiometric oxidant in the conversion of primary and secondary alcohols to carbonyl compounds. This procedure works efficiently at room temperature in almost all common solvents and neat in some cases. This process exhibits a very high degree of selectivity for the oxidation of primary alcohols to aldehydes, without any noticeable overoxidation to carboxyl compounds, and a high chemoselectivity in the presence of either secondary alcohols or of other oxidizable moieties. This procedure allows an easy, convenient, high-yielding method for the oxidation of alcohols starting from commercially available compounds.
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).
Catalyst-Free Imidation of Allyl Sulfides with Chloramine-T and Subsequent [2,3]-Sigmatropic Rearrangement
作者:Yubo Jiang、Fanyang Mo、Di Qiu、Chunxiang Kuang、Yan Zhang、Jianbo Wang
DOI:10.1002/cjoc.201200604
日期:2012.9
A facile synthesis of various allyl sulfonamides based on imidation of allyl sulfides with chloramine‐T and subsequent [2,3]‐sigmatropicrearrangement has been achieved without metal catalysts. The reaction completes smoothly within 10 min, providing excellent yields in environment friendly solvent of alcohol. Functional groups such as bromine, hydroxyl, protected amido and aldehyde are tolerant under
Dechalcogenative Allylic Selenosulfide and Disulfide Rearrangements: Complementary Methods for the Formation of Allylic Sulfides in the Absence of Electrophiles. Scope, Limitations, and Application to the Functionalization of Unprotected Peptides in Aqueous Media
作者:David Crich、Venkataramanan Krishnamurthy、Franck Brebion、Maheswaran Karatholuvhu、Venkataraman Subramanian、Thomas K. Hutton
DOI:10.1021/ja072969u
日期:2007.8.1
Primary allylic selenosulfates (seleno Bunte salts) and selenocyanates transfer the allylic selenide moiety to thiols giving primary allylic selenosulfides, which undergo rearrangement in the presence of PPh3 with the loss of selenium to give allylically rearranged allyl alkylsulfides. This rearrangement may be conducted with prenyl-type selenosulfides to give isoprenyl alkylsulfides. Alkyl secondary
Treatment of 3,4-epoxy-1-butene with CgF13I, PhSH, or Ph3GeH in the presence of Et3B provides 4-substituted-2-buten-1-ol in good yield. Et3B–Ph3SnH mediated intramolecular alkylation of 1,3-diene monoxide are also described.
The palladium-catalyzed arylation reaction of vinyl epoxides with organobismuthcompounds afforded the aryl-substituted (E)-allylic alcohols via ring opening of epoxides. Alternatively, the palladium-catalyzed reaction of diol acetonides and carbonates with bismuth derivatives afforded the aryl-substituted diol acetonides and carbonates without ring opening.
SET oxidation of bis-sulfinyl anions has enabled the uses of bis-sulfinyl radical as a synthetic equivalent of chiral acyl and methylene radicals involved in tandem reactions leading to the enantioselective construction of various carbo- and heterocyclic derivatives.