Tooru Kuroda

Reactions of alkenylchromium reagents prepared from alkenyl trifluoromethanesulfonates (triflates) with chromium(II) chloride under nickel catalysis

philicities in these complexes, with vanadium in complexes 4 and 5 exhibiting greater electrophilicity. Given the inclination of other 17-electron metal carbonyl complexes to undergo associative ligand displacement reactions, it seems ironic that the incorporation of a pentadienyl ligand, which would be expected to promote associative attack via

Selective grignard-type carbonyl addition of alkenyl halides mediated by chromium(II) chloride

73 coordination changes, should lead instead to a series of compounds for which much lower rates of substitution are observed and for which the substitutions also take place via dissociative means. Additional kinetic, EPR, and structural studies are under way in attempts to better understand the unexpected behavior of these 17-electron complexes.

Aldehyde-selective addition of alkynylchromium compounds prepared by reduction of alkynyl halides with chromium(II) reagent

Abstract Alkenyl (or aryl) iodide (or bromide) is readily reduced with CrCl2 is N,N-dimethylformamide at 25°C to gice the corresponding organochromium species which adds selectively to an aldehyde moiety without affecting the coexisting ketone or cyano group of the substrate.

2-Substituted 2,3-Dihydro-4H-1,3-benzoxazin-4-ones: A Novel Auxiliary for Stereoselective Synthesis of 1-.beta.-Methylcarbapenems

Abstract Alkynyl halides are reduced by chromium(II) chloride in DMF to give unisolable alkynylchromium compounds which add selectively to an aldehyde moiety without affecting the coexisting ketone group of the substrate.

A novel synthesis of a key intermediate for diltiazem

The dihydrobenzoxazone 9e, which is easily prepared from salicylamide 11 and cyclohexanone, serves as an efficient auxiliary in the synthesis of the 1-beta-methylcarbapenem key intermediate 10. The stereocontrolled Reformatsky-type reactions of the acetoxyazetidinone 2 with the carboximides 6 gave the intermediates 7 with high diastereoselectivities in high chemical yields. The auxiliary 9e also acts as a good leaving group in the TMSCl-promoted Dieckmann-type cyclization leading to a 1-beta-methylcarbapenem skeleton. By using this auxiliary, 10 was synthesized in 58% overall yield and four steps from 2.

A new synthesis of unsymmetrical diphenic acid derivatives: template-directed intramolecular Ullmann coupling reaction

Abstract A practical synthesis of methyl (2R,3S)-3-(4-methoxyphenyl)glycidate (−)-2a , a key intermediate for diltiazem ( 3 ), was described. Treatment of methyl (E)-4-methoxycinnamate (E)-1a with chiral dioxirane, generated in situ from a catalytic amount of an 11-membered C2-symmetric binaphthyl ketone 7a , provided (−)-2a in 78% ee and 89% yield. The crude mixture of (−)-2a and 7a was efficiently separated by the use of novel equipment performing continuous dissolution and crystallization to furnish the optically pure (−)-2a (>99% ee) and recovery of 7a in 64 and 88% yields, respectively.

A new stereocontrolled synthesis of diequatorial furofuran lignans having two different aryl groups : a synthesis of methyl piperitol

Abstract Intramolecular Ullmann coupling reaction of the diesters ( 6 , 9 ), which were prepared by regioselective acylation of salicyl alcohol by using the two different substituted 2-iodobenzoyl chlorides, afforded the unsymmetrical diphenic acid derivatives ( 7 , 10 ). Hydrogenolysis of the Ullmann coupling product ( 7 ) afforded the monoester ( 12 ) in an excellent yield.

An Improved Synthesis of ( E )-Cinnamic Acid Derivatives via the Claisen–Schmidt Condensation

Abstract Methyl piperitol, a representative example of the diequatorial furofuran lignans, was synthesized in a good overall yield based on a highly stereocontrolled tandem Michael addition-aldol reaction.

Asymmetric synthesis of methyl (2R,3S)-3-(4-methoxyphenyl) glycidate, a key intermediate of diltiazem, via Mukaiyama aldol reaction

Abstract A variety of (E)-cinnamic acid derivatives are prepared in high yields through the Claisen–Schmidt condensation in the presence of sodium metal and a catalytic amount of methanol with toluene employed as the co-solvent.

A new stereocontrolled synthesis of axial-equatorial furofuran lignans having two different aryl groups: A synthesis of Fargesin

Abstract Methyl (2R,3S)-3-(4-methoxyphenyl) glycidate, a key intermediate of diltiazem, was synthesized in good yield with high enantioselectivity based on chiral oxazaborolidine-mediated Mukaiyama aldol reaction of p-anisaldehyde with α,α-dichloro silyl ketene acetal (up to 96% ee), followed by reduction and cyclization.