Selective [5,5]‐Sigmatropic Rearrangement by Assembly of Aryl Sulfoxides with Allyl Nitriles

Abstract

Aromatic [5,5]-sigmatropic rearrangement is an appealing protocol for accessing 1,4-substituted arenes.H owever,s uch ap rotocol has not been well utilized in organic synthesis because of the difficulties in the synthesis of the substrates,s electivity issues,a nd limited substrate scope. Described herein is an ew [5,5]-sigmatropic reaction utilizing readily available aryl sulfoxides and allyl nitriles.This reaction features mild reaction conditions,high chemo-and regioselectivity,e xcellent functional-group compatibility,a nd broad substrate scope.Computational studies suggest that the success of the reaction can be attributed to the selective electrophilic assembly of the rearrangement precursors,i nw hich al inear -C = C = N-linkage favors [5,5]-sigmatropic rearrangement over the competitive [3,3]-sigmatropic rearrangement. Scheme 1. Backgrounda nd this work.

Construction of Biaryls from Aryl Sulfoxides and Anilines by Means of a Sigmatropic Rearrangement

“…When simple aniline ( 2 i ) was used as the coupling partner, [5,5] sigmatropic rearrangement from intermediate III competed with the [3,3] sigmatropic rearrangement, and a mixture of biaryls 3 ai and 3 ai′ was obtained in 46 % yield (Scheme ). Competition of [3,3] versus [5,5] sigmatropic rearrangements was also observed in our previous dehydrogenative coupling of aryl sulfoxides with phenols . Anilines 2 j and 2 k containing bromo and acetyl groups, respectively, at the ortho position also underwent [3,3] and [5,5] sigmatropic rearrangements to afford the corresponding biaryls as mixtures of the isomers.…”

Morita-Baylis-Hillman Type [3,3]-σ Rearrangment Enabled Z-Selective α-Arylation

“…Morita-Baylis-Hillman 型 [3,3] [4] . 其中, 浙江师 范大学化学与生命科学学院彭勃课题组提出"组装-脱 质子"的重排策略, 先后实现了芳基亚砜与烷基腈 [5] 、 烯丙基腈 [6] Morita-Baylis-Hillman (MBH)反应在有机合成反应 中有着广泛的应用. 该反应广为接受的机理包括四个步 骤, Michael 加成、Aldol 加成、分子内质子转移和最终 的 β-消除 [7][8][9] (Scheme 1b).…”

[3,3]- and [5,5]-Sigmatropic Rearrangements of Aryl Sulfoxides Using An ‘Assembly/Deprotonation’ Technology

“…Inspired by the success of the 'assembly/deprotonation' protocol, we switched from alkyl nitriles to allyl nitriles, achieving [5,5]-sigmatropic rearrangement of aryl sulfoxides (Scheme 2, eq 2). 16 In this Synpacts article, we highlight the 'assembly/deprotonation' strategy that has been used for the development of the above [3,3]-and [5,5]-sigmatropic rearrangement reactions (eqs 1 and 2, respectively).…”

“…employing lower temperatures and prolonging the reaction times (Tf 2 O, -60 °C, 18 h, then DABCO, -100 °C, 1 h) significantly improved the yield of 7aa from 39% to 84%. 16 As illustrated in Scheme 7, a wide variety of aryl sulfoxides 1 and allyl nitriles 5 proved to be suitable for the reaction. Similar to the above [3,3]-rearrangement (Scheme 5), the reaction also tolerated a wide variety of functional groups for both coupling partners (Scheme 7).…”