Synthesis of (Boryl)(silyl)iminomethanes by Insertion of Isonitriles into Silicon−Boron Bonds

Abstract

The insertion of alkyl and aryl isonitriles into the silicon-boron bond of silylboranes proceeded thermally to provide (boryl)(silyl)iminomethanes in moderate-to-good yields. The (boryl)(silyl)iminomethane reacted with borane (BH 3 ) to give the corresponding borane complex in good yield, whose crystal structure was determined by a single-crystal X-ray analysis.It is commonly known that multistep reactions of isonitriles with organoboranes involve the coordination of the isonitrile to the boron followed by alkyl migration from the boron to the isocyano carbon, leading to the formation of boron-and nitrogen-containing heterocycles. 1 A simple 1:1 insertion product of isonitrile with organoborane has been scarcely known, to our best knowledge. 2,3 Herein, we report a new insertion reaction of isonitriles into the silicon-boron bonds of silylboranes 4 to provide N-substituted (boryl)(silyl)iminomethanes in moderate-to-good yields. In contrast to our previous results involving silaborative reactions with carboncarbon multiple bonds, 5-7 our present research indicates that no transition-metal catalyst is needed for the silaboration of isonitriles. It is interesting to note that reactions of the N-substituted (boryl)(silyl)iminomethanes with BH 3 afforded chromatographically stable boraneimine complexes. The structure of the borane-imine complex was determined by a single-crystal X-ray analysis.The silylborane 1a was subjected to a reaction with an equimolar amount of tert-butyl isonitrile (2a) at room temperature. The product 3aa was isolated by bulb-to-(1) Casanova, J., Jr. In Isonitrile Chemistry; Ugi, I., Ed.; Academic Press: New York; 1971; p 109.(2) Reactions of isonitriles with B-H bonds of borazines and the B-B bond of tetrakis(dimethylamino)diborane were reported to afford monomeric (iminomethyl)borazines and iminobis(boryl)methanes, respectively: Meller, A.; Batka, H. Monatsh. Chem. 1970, 101, 648. (3) Monomeric imino(boryl)methanes were prepared by the reaction of (iminomethyl)lithium with chlorobis(dimethylamino)borane: Sicker,

Opportune gem‐Silylborylation of Carbonyl Compounds: A Modular and Stereocontrolled Entry to Tetrasubstituted Olefins

“…Suginome and Ito et al. found that the insertion of alkyl and aryl isonitriles into the silicon–boron bond of silylboranes could also proceed thermally to provide (boryl)(silyl)iminomethanes in moderate to good yields …”

“…Such reactivity was first observed by Buynak and Geng in 1995, [3] and is initiatedb yt he interaction of ethyl diazoacetate with the empty 3p orbital of the Ba tom in Me 2 PhSiÀBcat (Bcat = catecholboryl moiety) leading to an 'ate' complex. [5] Severali nteresting gem-silylborylations have been developed by reactiono fv inylic gem-dihalides with Me 2 PhSiÀBpin in the presence of lithiated bases (Scheme1a). [4] Suginome and Ito et al found that the insertion of alkyl and aryl isonitriles into the silicon-boronb ond of silylboranes could also proceedt hermally to provide (boryl)(silyl)iminomethanes in moderate to good yields.…”

“…[4] Suginome and Ito et al found that the insertion of alkyl and aryl isonitriles into the silicon-boronb ond of silylboranes could also proceedt hermally to provide (boryl)(silyl)iminomethanes in moderate to good yields. [5] Severali nteresting gem-silylborylations have been developed by reactiono fv inylic gem-dihalides with Me 2 PhSiÀBpin in the presence of lithiated bases (Scheme1a). This methodology,d evelopedb yH iyama and Shimizu, affords 1-boryl-1-silylallenes, [6] and 1-boryl-1-sylilalkenes.…”

Tandem Michael addition/isocyanide insertion into the C–C bond: a novel access to 2-acylpyrroles and medium-ring fused pyrroles

“…1 Among the isocyanide-based reactions, 1 isocyanide insertion reactions have attracted extensive attention in the past few decades. 2 A large number of N-heterocyclic compounds have been synthesized, involving isocyanide insertion into a heteroatom-H, 3 C-H, 4 C-O, 5 C-S, 6 C-Si, 7 Si-B, 8 Si-Si, 9 S-S, 10 CvM (M = metal), 11 Pd-C or Pd-heteroatom bond. 2,12 However, to our knowledge, the reaction involving isocyanide insertion into the C-C bond has not yet been reported.…”

Silylboranes as New Tools in Organic Synthesis

“…We found that insertion of alkyl and aryl isocyanides, which have a carbene-like divalent carbon atom, to the BÍSi bond of silylboranes proceeds thermally to give (boryl)(silyl)iminomethanes (Scheme 3). 12 The 1,1-silaboration of isocyanide may proceed through the initial coordination of the isocyanide to the boron atom of silylborane and subsequent migration of the silyl group from the boron to the isocyano carbon. The reaction rate was much influenced by the substituent on the boron atom: silylborane having dialkylamino groups showed much higher reactivity than the corresponding pinacol ester.…”