Chuzo Iwata

Enantioselective Cu-catalyzed 1,4-addition of Me3Al to a 4,4-disubstituted cyclohexa-2,5-dienone

Abstract A series of chiral enantiomerically pure 2-aryloxazolines was synthesized. (4 S )-2-(2′,6′-dimethoxyphenyl)-4-isopropyloxazoline proved to be an efficient chiral ligand for the Cu-catalyzed conjugate addition of Me 3 Al to cyclohexadienone, and by using 20mol% of this ligand, 1,4-adduct was obtained in 68% ee. In addition, TBDMSOTf is crucial for the asymmetric conjugate addition to proceed with good chemical yield and high ee.

Intramolecular michael addition reaction to chiral vinylic sulfoxides. An enantioselective synthesis of (R)- and (S)-1,7-dioxaspiro[5.5]undecane

Abstract (R)- and (S)-1,7-Dioxaspiro[5.5]undecane ((R)- 1 and (S)- 1 ), sex pheromone of an olive fly, was each stereoselectively synthesized using an intramolecular Michael addition of hydroxyl group to a chiral vinylic sulfoxide moiety as an asymmetric induction step.

A new and facile route to spiro-ketal skeleton via highly stereoselective CO bond formation by intramolecular Michael addition to δ,β-unsaturated sulfoxides

Abstract Diastereoisomerically pure ( E )-and ( Z )-2-methyl-1,6-dioxaspiro [4.5]-decane (insect pheromone) was efficiently prepared via a highly stereo controlled intramolecular Michael addition of hydroxyl group to an unsaturated sulfoxide moiety during the crucial cyclization step.

Asymmetric total synthesis of halicholactone

The asymmetric total synthesis of the marine metabolite, halicholactone 1, is described. The bisallylic triol 6 with three chiral centers at C8, C12, and C15 was constructed by [2,3]-sigmatropic rearrangement of the sulfoxide 18, which was prepared stereoselectively using the chirality of (diene)Fe(CO)3 complexes. Introduction of the trans-substituted cyclopropane subunit into 21 was successfully achieved using the modified regio- and stereoselective Simmons-Smith reaction. The use of RCM (ring-closing metathesis) methodology (4-->35) was pivotal for the formation of a nine-membered unsaturated lactone fragment of halicholactone 1. As this approach is flexible and stereoselective, other oxylipins could be synthesized by the protocol described herein.

Stereoselective synthesis of all isomers of 2-methyl-1,6-diaxaspiro[4.5]decane (insect pheromone) using a chiral sulfoxide auxiliary

Abstract All four isomers of 2-methyl-1,6-dioxaspiro[4.5]decane were synthesized stereoselectively by means of successful asymmetric induction using only a chiral sulfoxide auxiliary.

Asymmetric synthesis of (diene)Fe(CO)3 complexes by a catalytic enantioselective alkylation using dialkylzincs

Abstract The reaction of meso-(2, 4-hexadien-1, 6-dial)Fe(CO)3 complex1 with several alkylzincs in the presence of 50 mol% of(S)-(+)-diphenyl(1-methylpyrrolidin-2-yl)methanol6a proceeded with high enantiotopic group- and diastereotopic face-selectivity to give(2R, 6S)-alcohol complexes2a-c as major products, except in the case with dimethylzinc (>90% de and >98% ee). On the other hand, the methylation of1 with Me2Zn proceeded with high enantioselectivity by adding 1.8 equiv. ofTi(Oi-Pr)4 in the presence of 3 mol% of(S, S)-1, 2-bis(trifluoromethylsulfonamide)cyclohexane9a (82% de, 96% ee). The enantioselective alkylation was also applied to the kinetic resolution of racemic (sorbic aldehyde)Fe(CO)3 complex10. Download : Download full-size image

Diastereoselective [4 + 2] type cycloaddition of 1-azatriene iron-tricarbonyl complex: Asymmetric synthesis of a piperidien alkaloid

A LiClO4 catalyzed cycloaddition reaction of 1-azatriene iron-tricarbonyl complex 2b with Danishefskys diene proceeds in highly stereoselective manner to give diastereomerically pure 2-substituted dehydropiperidinone derivative 3b. The chiral cycloadduct 3b* is converted into a biologically active piperidine alkaloid SS20846A in 3 steps, by which its absolute configuration is revealed as 2S,4S.

Asymmetric induction by sulfinyl chirality: a total synthesis of (+)-talaromycin A and (−)-talaromycin B

Abstract A total synthesis of (+)-talaromycin A and (−)-talaromycin B was accomplished by means of successive asymmetric induction of all chiral centers using a chiral sulfinyl group.

ASYMMETRIC SYNTHESIS OF (DIENE)FE(CO)3 COMPLEXES VIA CATALYTIC ENANTIOSELECTIVE ALKYLATION WITH DIALKYLZINC

The reaction of meso-2,4-hexadien-1,6-dial Fe(CO)3 complex 1 with several alkylzincs in the presence of 50 mol% of (S)-(+)-diphenyl-(1-methylpyrrolidin-2-yl) methanol 4a proceeded with high enantiotopic group- and face-selectivity to give (2R,6S)-mono alcohol complexes 2a-c as major products (>90% de and >98% ee).

Absolutely diastereoselective 1,2-nucleophilic addition of organometallic reagents to imines using diene-iron tricarbonyl chirality

Abstract 1-Imino- E , E -butadiene-iron tricarbonyl complex 1 reacts with various organometallic nucleophiles in a stereoselective manner, and especially by use of organocerium reagents, only single diastereomers 2 were obtained in good yields.