AlCl₃-Catalyzed Hydrosilylation of Alkynes with Hydropolysilanes

Abstract

AlCl 3 catalyzes addition reactions of hydrooligosilanes (H(SiMe 2 ) n R; n = 2-4, R = H, Me, Ph) with 1-decyne and other alkynes under mild conditions. In most reactions the Si-Si bonds remain intact to form anticipated products in fair to excellent yields, although Si-Ph bonds appear to be cleaved partially under the conditions. Arylethynes tend to form abnormal products due to Si-Si bond scission, but at a low temperature, the addition reaction proceeds normally. The reaction of 1,2-dihydrotetramethyldisilane with 1-decyne furnishes 1,2-didecenyldisilane, 1,3-didecenyltrisilane, and other byproducts at 0 °C, while the reaction run at a lower temperature proceeds cleanly. 1,3-Dihydrohexamethyltrisilane reacts more cleanly even at 0 °C. The reaction of pentamethyldisilane with 1,6-heptadiyne proceeds in a different direction, leading to cyclization. 1,7-Octadiyne reacts with 1,3-dihydrohexamethyltrisilane to give a polymeric material. The reaction of 1,2,3-trihydropentamethyltrisilane or poly(phenylsilylene) with 1-dectyne proceeds cleanly without perceptible Si-Si bond cleavage. IntroductionHydrosilylation is a long-known reaction and is an indispensable tool to create a silicon-to-carbon bond. 1 The majority of precedents deal with reactions with hydromonosilanes such as trichlorosilane, phenyldimethylsilane, trimethoxysilane, and diphenylsilane. As far as transition metal-catalyzed hydrosilylation is concerned, the reaction with a hydrooligosilane, H(SiMe 2 ) n R, has been believed to be a rather tough and intricate task due to the Si-Si bond cleavage, 2 although very few successful examples have been encountered incidentally. 3 For instance, Urenovitch and West reported long ago that attempted platinum-catalyzed reaction of 1-octene with pentamethyldisilane gave trimethylsilane and a trace of octyltrimethylsilane. 4 Besides transition metal complexes, Lewis acids are also known to catalyze the hydrosilylation with hydromonosilanes. 5 Rosenberg and co-workers have reported Lewis acid-catalyzed reactions of thiobenzophenone, thiols, phenols, thiophenols, aldehydes, and R-diketones with hydrodisilanes. 6 However, Lewis acid-catalyzed reactions of hydrooligo-and hydropolysilanes with unsaturated carbon linkages have not been documented. 7 This article discloses that AlCl 3 is a capable catalyst to promote the addition of hydrooligosilanes and hydropolysilanes to alkynes without deterioration of the silicon chain under carefully tuned conditions. A possible side reaction, which we have to keep in mind beforehand, is skeletal rearrangement of Si-Si chains. 8 In the present study, such a † Part of the Dietmar Seyferth Festschrift.

Intermolecular interactions in group 14 hydrides: Beyond CH···HC contacts

“…An interesting example is the crystal structure of hexyl‐heptahydro‐octasilasesquioxane (lijgug), with a practically collinear O 3 SiH···HSiO 3 moiety ( 3 ) showing a H···H distance of 2.34 Å. For silicon, an angular dependence of the R 3 SiH···HSiR 3 contact distances is seen in the CSD (Figure ), whereby the closer the two interacting silyl groups are to being colinear (measured by the average SiH···Si angle), the shorter the H···H distance can be, with several nearly collinear contacts being at distances shorter than 2.8 Å …”

“…For silicon, an angular dependence of the R 3 SiAHÁÁÁHASiR 3 contact distances is seen in the CSD (Figure 1), whereby the closer the two interacting silyl groups are to being colinear (measured by the average SiAHÁÁÁSi angle), the shorter the HÁÁÁH distance can be, with several nearly collinear contacts being at distances shorter than 2.8 Å. [41,[57][58][59][60][61] A similar analysis of the GeAHÁÁÁHAGe contacts discloses a group of structures (fibpub, [62] kajzok, [63] GeD 4 , [64] pallev, [65] larpid, [66] qelyip, [67] papzai [68] ) with GeÁÁÁGe distances shorter than the van der Waals radii sum (4.58 Å) that may or may not show simultaneous short GeÁÁÁH (< 3.49 Å) contacts, but all of them have HÁÁÁH contacts longer than 2.7 Å. In most cases the interaction topology is of type 2 involving GeH 3 or GeH 2 groups, while in one case (fibpub) [62] a 3:3 staggered conformation 4, in another case the 1 type interaction (qelyip), [67] and in yet another case a colinear 3 interaction (papzai) [68] is found.…”

Stepwise Introduction of Different Substituents to α-Chloro-ω-hydrooligosilanes: Convenient Synthesis of Unsymmetrically Substituted Oligosilanes

“…A problem to be overcome is limitation of facile functionalization of the hydrosilane moiety in the oligosilanes. Thus far, halogenation [14][15][16], Lewis acid-catalyzed reactions [17][18][19] and radical-promoted reactions [20][21][22][23][24] have been used for the Si-H modification of hydrooligosilanes. Transition metal-catalyzed reactions of hydrosilanes are well known as Si-H conversion methods, including hydrosilylation [25][26][27], dehydrogenative silylation of OH and NH groups [28][29][30][31], silylation of aromatic rings [32][33][34][35][36] and so on.…”

Synthesis of 1,2,3,4-Tetrahydroquinolines Using AlCl3in Aqua Mediated

“…Lately, AlCl 3 has been employed for the synthesis of 5benzoylacenaphthene, 15 selective synthesis of 2-aryl-2H-and 4-aryl-4H-3,5-diformylpyrans from acetal with aromatic aldehydes, 16 catalytic asymmetric arylation of aldehydes, 17 cat-alytic beckmann rearrangement of ketoximes, 18 conversion of isopropenyl acetate into 3-acetyl-and 3,5-diacetyl-2,6dimethyl-4H-pyran-4-ones, 19 one-pot four-component synthesis of 1,4-dihydropyridines and their aromatization, 20 hydrosilylation of alkynes with hydropolysilanes, 21 cycloadditions of activated cyclopropanes and aromatic aldehydes, 22 synthetic routes to sterically hindered unsymmetrical diaryl ketones via arylstannanes, 23 one-pot preparation of 1,1,3triheteroaryl compounds of crotonaldehyde and indole, 24 1substituted 1,2,3,4-tetrahydrobenz[g]isoquinoline-5,10diones, 25 synthesis of 5-amino-4-arylazo-3-methyl-1Hpyrazoles and 5-aryl-3-methylpyrazole[3,4-e] [1,2,3,4] tetrazines 26 and oxidation of alcohol. 27 The replacement of environmental hazardous catalysts in various processes, with green catalysts, solvent-free and on water reaction is of the innovative trends.…”