Shin-ichi Inaba

Asymmetric synthesis of β-lactams. II. Highly effective asymmetric induction by means of “titanium template”

Abstract The reaction of dimethylketene methyl trimethylsilyl acetal with the Schiff bases of chiral α-amino esters in the presence of titanium tetrachloride gave the corresponding β-lactams with extremely high stereoselectivity (up to > 99% diastereomeric purity). Possible mechanism for the highly effective asymmetric induction using “titanium template” is proposed.

Asymmetric synthesis of β-lactams. I. The reaction of dimethylketene silyl acetal with (S)-alkylidene(1-arylethyl)amines promoted by titanium tetrachloride

Abstract Asymmetric synthesis of β-lactams by means of the reaction of dimethylketene silyl acetal with (S)-alkylidene(1-arylethyl)amines in the presence of titanium tetrachloride was studied. The extent of the asymmetric induction was in the range of 44–78% (diastereomeric purity 72–89%) and the (S)-configuration was turned to be preferentially induced at the 4 C position of the resulting β-lactams.

Metallic nickel as a reagent for the coupling of aromatic and benzylic halides

Abstract The oxidative addition of aromatic and benzylic halides to activated metallic nickel occurred under mild conditions to give the corresponding dehalogenative coupled products in good yields.

Reduction of isocyanates and carbodiimides via hydrosilylation

Abstract The hydrosilylation of isocyanates is promoted by palladium catalysts and affords N-silylformamides or C-silylamides. The orientation of the reaction depended upon the structure of isocyanates. The reaction of carbodiimides with silicon hydrides, catalyzed by PdCl 2 or (Ph 3 P) 3 RhCl, required higher temperatures to give N-silylformamidines. The adducts obtained in these reactions are precursors to formamides, formamidines, and their N-acetyl derivatives.

Reformatsky type additions of haloacetonitriles to aldehydes mediated by metallic nickel

Abstract Nickel in the metallic state was found to carry out the Reformatsky type addition of haloacetonitriles to aldehydes via cyanomethylnickel halides to give β-hydroxynitriles in good yields.

Syntheses of N-silylformamidines by the hydrosilylation of carbodiimides

The hydrosilylation of carbodiimides was found to proceed at higher temperatures in the presence of catalytic amounts of palladium chloride or tris-(triphenylphosphine)chlororhodium to afford N-silylformamidines in high yield. These were found to be good precursors to formamidines and N-acetyl-formamidines.

Metallic nickel: A coupling reagent of benzyl halides and acyl halides to yield benzyl ketones

Abstract Metallic nickel was found to be a convenient reductive coupling reagent for the preparation of benzyl ketones by the reaction of benzyl halides with acyl halides.

Reaction of trimethylsilyl cyanide with isocyanates and carbodiimides

Trimethylsilyl cyanide reacts with isocyanates to give 12 cycloadducts, 5-(trimethylsilylimino)imidazolidine-2,4-diones, in high yield. The reaction of trimethylsilyl cyanide with carbodiimides proceeded in the presence of a catalytic amount of aluminum trichloride to afford 11 adducts, N-trimethylsilyl-1-cyanoformamides. At rather high temperatures, the reaction also proceeded without catalyst. The adducts were further allowed to react with isocyanates and carbodiimides to yield 4-imino-5-(trimethylsilylimino)imidazolidin-2-ones and 2,4-diimino-5-(trimethylsilylimino)imidazolidines, respectively. On the other hand, the reaction of trimethylsilyl cyanide with methyl isothiocyanate gave a novel cycloadduct, 4-cyano-5-bis(trimethylsilyl)aminoimidazolidine-2-thione.

Reactions of hydropolysilanes with alcohols catalysed by tris(triphenylphosphine)chlororhodium

Abstract [RhCl(PPh3)3] is a very effective catalyst for the cleavage of Si-Si bonds by alcohols.

Reaction of trimethylsilyl cyanide with carbodiimides

Abstract Trimethylsilyl cyanidereact with carbodiimides in the presence of aluminum trichloride to give 1 1 adducts, N-trimethylsilyl-1-cyanoformamidines (I), in high yields. At rather high temperatures (150–200 °C) the reaction also proceeded without catalyst. The 1 1 adduct reacted with isocyanates and carbodiimides forming 4,5-diiminodiazolidine-2-one and 2,4,5-triiminoimidazolidine, respectively.