Rhodium cyclobutanol

Under H2, the rhodium(I)-catalyzed C-C bond cleavage reaction of cyclobutanone 73 afforded ring-opened alcohol 74 (Scheme 3.42). Based on the state-of-the-art knowledge of cyclobutanone/cyclobutanol chemistry, we may assume that hydrogenolysis proceeds through ring opening of rhodium cyclobutanolates by P-carbon elimination. 

Simiraly, alkynones undergo arylative cyclization with arylboronic acids in the presence of a rhodium catalyst (Equation (49)).400 When acetylenic /3-keto esters are employed as shown in Equation (50), arylative cyclization (formation of cyclobutanols) and subsequent, facile acid-catalyzed bond cleavage take place to give <5-keto esters.401 Ring expansions of cyclic [3-keto esters are also possible according to this reaction. 

Intramolecular C—H insertion, on the other hand, is already a practical alternative for the constmction of cyclobutanols, P-lactams - and of cyclopentane-containing targets. With regard to the latter, diazo transfer can be effected on a large scale with the inexpensive methanesulfonyl azide. The rhodium carboxylate catalysts are effective at very low concentration (<1 mol %) and can easily be recovered from the reaction mixture, if desired. ... 

Ishida, N. Sawano, S. Murakami, M. Synthesis of 3,3-Disubstituted [Small Alphaj-Tetralones by Rhodium-Catalysed Reaction of l-(2-haloaryl) Cyclobutanols. Chem. Commun. 2012,48,1973-1975. 

Seiser, T. Roth, O. A. Cramer, N. Enantioselective Synthesis of Indanols from tert-Cyclobutanols Using a Rhodium-Catalyzed C-C/C-H Activation Sequence. Angew. Chem., Int. Ed. 2009,48,6320-6323. 

In 2008, Cramer described a rhodium(I)-catalyzed enantioselective rearrangement of allenyl cyclobutanols (Scheme 10) [44]. The formation of rhodium(I)-aUcoxide 35 triggered a / -carbon elimination, providing the corresponding aUcyl-rhodium... 

Scheme 10 Enantioselective rhodium(I)-catalyzed rearrangement of allenyl cyclobutanols...

Scheme 11 Extension of the rhodium(I)-catalyzed /J-carbon elimination to vinyl cyclobutanols and to domino processes...

Seiser T, CramerN (2010) Rhodium(I)-catalyzed enantioselective activation of cyclobutanols formation of cyclohexane derivatives with quaternary stereogenic centers. Chem-Eur J 16(11) 3383-3391. doi 10.1002/chem.200903225... 

Seiser T, Roth OA, Cramer N (2009) Enantioselective synthesis of indanols from tert-cyclobutanols using a rhodium-catalyzed C-C/C-H activatirai sequence. Angew Chem Int Ed 48(34) 6320-6323. doi 10.1002/anie.200903189... 

Seiser T, Cathomen G, Cramer N (2010) Enantioselective construction of indanrates fiorn cyclobutanols using a rhodium-catalyzed C-C/C-H/C-C brurd activation process. Synlett 11 1699-1703. doi 10.1055/s-0029-1219959... 

Transition metal alkoxides of tert-cyclobutanols undergo ring opening by P-carbon elimination to generate ketones that are metalated at the y-position these can be utilized in many functionalization reactions. Palladium, rhodium, and nickel have been the most studied metals in these transformations. Useful transition metal cyclobutanolates are generated from either cyclobutanones or cyclobutanols. 

Monosubstituted cyclobutanones reacted with arylboronic acids in the presence of a Rh(I)-P(f-Bu)3 catalyst to afford butyrophenone derivatives by the addition of an arylrhodium(I) species to the carbonyl group, followed by ring opening of the resulting rhodium(I) cyclobutanolate by P-carbon elimination... 

Asymmetric ring-opening reorganization of cyclobutanol 42 proceeded via 1,4-rhodium migration to give 1-indanone 43 in a diastereo- and enantioselective manner (Scheme 3.24) [35]. 

The alkylrhodium(I) species formed by ring opening of 3-(2-silylphenyl)-cyclobutanol 44 underwent a 1,4-rhodium/silicon exchange to generate... 

Rhodium(I)-catalyzed reactions of l-(2-bromophenyl)cyclobutanol 47a afforded a 3,3-disubstituted 1-tetralone 48a (Scheme 3.27) [37]. The reaction was proposed to involve oxidative addition of the aryl-Br bond to the alkox-orhodium(I) species, followed by P-carbon elimination. Azetidin-3-ol 47b could be used instead of cyclobutanols to furnish isoquinolinone 48b. 

Very recently, Compain proposed an approach to spirocyclic imino sugars (Scheme 41). The synthetic route started from known cyclobutanol 208, which was transformed into carbamate 209. Rhodium-catalyzed intramolecular C-H amination performed on that compound led to oxazolidinone 211. Subsequently, this compound was Al-allylated and subjected to the ring-closing metathesis with the Grubbs II cat. As a... 

Rhodium catalysis allows the formation of 3,3-disubstituted a-tetralones from l-(2-haloaryl)cyclobutanols. The reaction is likely to involve a five-membered rho-dacycle (94), followed by opening of the four-membered carbocyclic ring to give a seven-membered rhodacycle (95). The tetralone product is formed following reductive... 

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