Diastereomer-Differentiating Radical β-Addition to 4- or 5-Methyl-2-[(2,4,6-triisopropylphenyl)sulfinyl]-2-cyclopentenones

Abstract

Addition of alkyl radicals to a diastereomeric mixture of (4R)- and (4S)-4-methyl-2-[(2,4,6-triisopropylphenyl)sulfinyl]-2-cyclopentenones gave the diastereomerically pure addition product derived from the (4R)-isomer, while the (4S)-isomer remained unreacted. The tert-butyl radical addition to a diastereomeric mixture of (5R)- and (5S)-5-methyl-2-[(2,4,6-triisopropylphenyl)sulfinyl]-2-cyclopentenones also gave the diastereomerically pure addition product. These results show that (4R) and (4S) or (5R) and (5S) diastereomers were kinetically separated in the radical β-addition. The 1,2- and 1,3-steric interactions in the radical addition to 4- or 5-methyl-2-cyclopentenones were also examined.

Recent developments in chiral non-racemic sulfinyl group chemistry in asymmetric synthesis

“…Additionally, addition of alkyl radicals to diastereomeric mixtures of 4-or 5-methyl substituted 2-(Arylsulfinyl)-2-cyclopentenones leads to a kinetic resolution of the two diastereoisomers. 149 The sulfinyl group has been used to successfully control the stereochemistry of conjugate additions of arylcopper reagents to distant enones. 150 2-sulfinylpyrrole-derived cinnamides 182 undergo conjugate addition with aryl Grignard reagents in the presence of copper(I) iodide with high 1,6-induction (Scheme 82).…”

New Asymmetric Reactions of 2-Formyl- and 2-Acyl-1-[(2,4,6-triisopropylphenyl)sulfinyl]naphthalenes via Diastereomeric Rotamers

“…To avoid the racemization of the sulfoxide, the reaction was immediately quenched after the addition of the precooled solution of ( R )-diacetone d -glucosyl 2,4,6-triisopropylbenzenesulfinate to lithiated 1 in one portion at −105 °C. This gave a 98% yield of sulfoxide ( R )- 2c with 98% ee .…”

Acylvinyl and Vinylogous Synthons

“…All kinds of electrophiles have been employed with these equivalents, − which have been used, for example, in the stereospecific total synthesis of cyclopentanoid antibiotics (±)-pentenomycins I−III ( 66 ), their epimers ( 67 ), and dehydropentenomycin I ( 68 ) via alcohol 65 40 as common synthetic precursor , (Scheme ). Also, α-bromoketal 69 can be lithiated and treated with propylene oxide affording alcohol 70 , which is transformed into enone 71 (Scheme ), an intermediate in the synthesis of the macrocyclic diterpenes (±)- epi -jatropone and (±)-jatropone …”