Rhodium asymmetrical ring-opening reaction

Sulfur nucleophiles are also able to afford 2-sulfanyl-l,2-dihydronaphthalen-l-ols such as 276 via rhodium catalyzed asymmetric ring-opening reactions, as shown in Equation (163) <2004JOC2194>. 

Lautens M, Fagnou K (2001) Effects of halide ligands and protic additives on enantioselectivity and reactivity in rhodium-catalyzed asymmetric ring-opening reactions. J Am Chem Soc 123 7170-7171... 

Rhodium-catalyzed asymmetric ring-opening reactions of 1,4-epoxy-1,4-... 

Rhodium catalysts have also been used with increasing frequency for the allylic etherification of aliphatic alcohols. The chiral 7r-allylrhodium complexes generated from asymmetric ring-opening (ARO) reactions have been shown to react with both aromatic and aliphatic alcohols (Equation (46)).185-188 Mechanistic studies have shown that the reaction proceeds by an oxidative addition of Rh(i) into the oxabicyclic alkene system with retention of configuration, as directed by coordination of the oxygen atom, and subsequent SN2 addition of the oxygen nucleophile. 

Other Related Reactions In addition to simple 1,4-addition reactions described so far, other related rhodium-catalyzed asymmetric carbon-carbon bond-forming processes have also been developed. Lautens reported an asymmetric ring-opening of... 

Mirkin and coworkers reported on catalytic molecular tweezers used in the asymmetric ring opening of cyclohexene oxide. In this case the early transition metal is the catalyst and rhodium functions as the structural inductor metal. The catalyst consists of two chromium salen complexes, the reaction is known to be bimetallic, and a switchable rhodium complex, using carbon monoxide as the switch. Indeed, when the salens are forced in dose proximity in the absence of CO the rate is twice as high and the effect is reversible [77]. 

Murakami [27] and Lautens [28] independently reported the rhodium-catalyzed addition of arylboronic acids to oxanorbornenes (Scheme 3.12). Murakami reported that the reaction of oxabenzonorbornadiene 37 a with phenylboronic acid 2m, in the presence of a rhodium-P(OEt)3 catalyst in MeOH at reflux, gave an 86% yield of the ring-opened alcohol 38 am. Lautens reported the asymmetric version of the reaction, where high enantioselectivity was observed with chiral ferrocenylbisphosphine hgand 39 in a... 

Arenes suffer dearomatization via cyclopropanation upon reaction with a-diazocarbonyl compounds (Btlchner reaction) [76]. Initially formed norcaradiene products are usually present in equilibrium with cycloheptatrienes formed via electrocyclic cyclopropane ring opening. The reaction is dramatically promoted by transition metal catalysts (usually Cu(I) or Rh(II) complexes) that give metal-stabilized carbenoids upon reaction with diazo compounds. Inter- and intramolecular manifolds are known, and asymmetric variants employing substrate control and chiral transition metal catalysts have been developed [77]. Effective chiral catalysts for intramolecular Buchner reactions include Rh Cmandelate), rhodium carboxamidates, and Cu(I)-bis(oxazolines). While enantioselectivities as high as 95% have been reported, more modest levels of asymmetric induction are typically observed. 

---