SULFURANES .6. REACTIONS INVOLVING ALKOXY LIGANDS OF DIALKOXYDIARYLSULFURANES - FORMATION OF OLEFINS AND ETHERS
SULFURANES .6. REACTIONS INVOLVING ALKOXY LIGANDS OF DIALKOXYDIARYLSULFURANES - FORMATION OF OLEFINS AND ETHERS
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DOI：
10.1021/ja00769a036
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发表时间：
1972-01-01
影响因子：
15
通讯作者：
MARTIN, JC
中科院分区：
文献类型：
--
作者：
ARHART, RJ;MARTIN, JC
Dehydrations of secondary and tertiary carbinols with 1 [(C6H5) 2S (ORf) 2, where Rf= C6H5C (CF3) 2] proceed under unusually mild conditions to give generally excellent yields of olefin. The synthetic utility of the reaction is demonstrated by the formation of the hitherto inaccessible unrearranged olefin from the dehydration of tricyclopropylcarbinol (5). Tertiary alcohols are dehydrated essentially instantaneously, even at—50 in ether or chloroform. The kinetic isotopeeffect (ku/ko— 1.54) for the intramolecular competitionin the dehydration of partially deuterated tert-butyl alcohol, when considered with evidence for carbonium ion rearrangements in certain cases, favors a mechanism with considerable El character. A strong preference for trans coplanar disposition of leaving groups in the dehydration of appropriately chosen secondary carbinols gives evidence for the E2 character in these reactions. Primary alcoholsreact with 1 to form unsymmetrical ethers (RfOCH2R) in the absence of structural features increasing the acidity of ß protons. The rate of this reaction with various alcohols (CH3OH>(CH3) 2CH-CH2OH>(CH3) 3CCH2OH) is that expected for an Sn2 displacementby RfO~ on an intermediate, postulated to be the alkoxysulfonium ion (ROS (CeH5) 2+), formed by reaction of the alcohol with 1. A similar intermediate is implicated in the dehydration reactions of tertiary and secondary alcohols. The exchange of alkoxy ligands of 1 with added alcohols is shown by nmr to be fast. Reactions of chloroformsolutions of 1 with alcohols, such as neopentyl alcohol, which do not give rapid elimination or ether-forming reactions, lead by a radical-chain process to RfOCCIs. In thisreaction 1 acts as an oxidizing agent.
