Meta- andPara-Difunctionalization of Arenes via a Sulfoxide−Magnesium Exchange Reaction

Abstract

The aryl sulfoxide moiety (ArSO) allows an expedient two-step meta-, para-difunctionalization of readily available diaryl sulfoxides. In the first step, the sulfoxide plays the role of a directing metalation group. In the second step, triggered by i-PrMgCl x LiCl, it becomes a leaving group and undergoes a regioselective sulfoxide-magnesium exchange.

Highly Regioselective Preparation of Heteroaryl–Magnesium Reagents by Using a Br/Mg Exchange

“…The direct reaction of 4-methoxybenzenesulfinyl chloride (4 q) with the heterocyclic magnesium species furnished the sulfoxides 14 f and 14 m in 70-94 % yield ( Table 5, entries 6 and 13). [12] It is worth mentioning that the Br/Mg-exchange reaction of 2,5-dibromo-3-methoxythiophene with the bulky reagent 1 c·L 2 led to the formation of the 2-magnesium-substituted thiophene (12 f; Table 5, entries [14][15][16] and not to the 5magnesium-substituted product (as occurs for the reactions of the other dibromothiophene derivatives 11 a-c and 11 e). We assume that this selectivity resulted from a preliminary coordination of the bulky magnesium reagent to the oxygen of the methoxy substituent.…”

Regio‐ und chemoselektive Metallierung von Arenen und Heteroarenen mit gehinderten Metallamidbasen

“…[142] In ähnlicher Weise gelingt mit TMPMgCl·LiCl (2) die glatte Magnesierung von vielfältigen aromatischen Sulfonen. [143,144] Gleichfalls ermçglicht 2 die Deprotonierung von funktionalisierten cyclischen und acyclischen Verbindungen. [145,146] 4 ], 25 8C, 1 h) ergibt das trisubstituierte Furan 142 in 77 % Ausbeute.…”

Stereoselective synthesis of tetrasubstituted alkenes via a sequential carbocupration and a new sulfur–lithium exchange

“…Sulfur–lithium exchanges proceed only readily with sulfoxides [17–19] and these reactions are often complicated by radical side reactions [20–21]. This new, direct sulfur–lithium exchange on an alkenyl thioether of type 4 involves the use of a bromobiphenyl R-group, which by treatment with BuLi at low temperatures, undergoes first a fast bromine–lithium exchange leading to an intermediate biphenyllithium derivative of type 6 , followed by an intramolecular ring-closing sulfur–lithium exchange [22] leading to the desired alkenyllithium 7 (Scheme 2).…”