The first samarium(ii)-mediated stereoselective spirocyclization onto an aromatic ring

Abstract

The first samarium(II)-mediated spirocyclisation onto an aromatic ring was achieved by the reaction of methyl 4-(4-oxoalkyl)benzoates with SmI2 in the presence of i-PrOH and HMPA, yielding methyl 1-alkyl-1-hydroxyspiro-[4.5]dec-6-ene-8-carboxylates in moderate to high yields.

Development of Useful Reactions Involving Tandem Cyclizations Based on the Novel Reactivities of Allenic Compounds

“…Although space restriction does not permit a detailed description, our group developed some other interesting novel reactions such as (1) stereoselective synthesis of 1,3-amino alcohols via allenylindium reagents using 2-ethynylaziridines as chiral carbon nucleophiles, 143,144) (2) samarium(II)-mediated radical cyclization onto an aromatic group, [174][175][176][177][178] (3) synthesis and isomerization of vinylaziridines and their application to the stereoselective synthesis of (E)-alkene dipeptide isosteres. [64][65][66][67]179,180) The author hopes the presented reactions based on the novel reactivities of allenes will facilitate further development of allene chemistry [181][182][183] and application to synthesis of pharmacologically important compounds from this class of compounds.…”

Benzylic Boron Reagents Behaving as Allylic Boron Reagents towards Aldehydes: A New Asymmetric Reaction Leading to Homoallylic Alcohols with Concomitant Dearomatisation

“…The dry ice/acetone bath was removed and the reaction mixture was stirred at room temperature until starting aldehyde is consumed by TLC (6 h). Saturated NH 4 Cl solution was then added and the mixture was extracted with EtOAc. The combined organic layers were dried over …”

“…[4] During the course of certain mechanistic studies (see later) we have discovered a new dearomatisation reaction in which benzylic boron substrates essentially behave as allylic boron reagents in reactions with aldehydes leading to cyclohexenones in high d.r. and e.r.…”

Regioselective Samarium Diiodide Induced Couplings of Carbonyl Compounds with 1,3‐Diphenylallene and Alkoxyallenes: A New Route to 4‐Hydroxy‐1‐enol Ethers

“…Similar samarium diiodide promoted cyclizations of g-aryl-substituted ketyls to give spirocyclic compounds have recently been described by Berndt [36] and Tanaka. [37] However, in the case of 27 and 28 the precursor for the cyclization is an alkenyl radical which is formed in situ by samarium diiodide induced coupling of 25 and 8 b. The proposed mechanism for this cascade reaction is presented in Scheme 11.…”