Efficient Transition Metal-Catalyzed Reactions of Carboxylic Acid Derivatives with Hydrosilanes and Hydrosiloxanes, Afforded by Catalyst Design and the Proximity Effect of Two Si–H Groups

Abstract

The discovery of the ruthenium cluster μ₃,-(η²:η³:η⁵-acenaphythylene)Ru₃(CO)₇ (1), which is active in catalytic reactions involving Si–H bond activation, and the rate enhancement by the proximity effect of two Si–H groups enabled the reduction of carboxylic acid derivatives with hydrosilanes under mild reaction conditions. A judicious choice of the hydrosilane and of the additives led to a remarkably selective reduction. Besides simple reduction, the treatment of carboxylic acid derivatives with hydrosilanes in the presence of 1 led to new reactions involving several C–O and C–C bond-forming as well as C–O bond-cleavage steps. These reactions included polymerization, rearrangement, and aromatic substitution. The use of inexpensive 1,1,3,3-tetramethyldisiloxane (TMDS) facilitated the efficient reduction of amides to amines using either 1, commercially available platinum compounds, or environmentally friendly iron complexes. The conversion of tertiary amides into aldenamines was achieved by iridium catalysis. In the ruthenium-, iridium-, platinum-, and iron-catalyzed reduction of amides, the use of the reducing reagent polymethylhydrosiloxane (PMHS) resulted in self-encapsulation of the residual metal species into the formed silicone gel to give the ‘metal-free’ product in a straightforward way.

1 Introduction

2 Two Key Preliminary Investigations

2.1 A Ruthenium Cluster for Si–H Bond Activation

2.2 Proximity Effect of Two Si–H Groups for Rate Enhancement

3 Ruthenium-Catalyzed Reduction of Carboxylic Acid Derivatives

3.1 From Ketones to Less Reactive Carboxylic Acid Derivatives

3.2 Self-Encapsulation of the Residual Metals into Silicone Gel

4 Extension to C–O and C–C Bond-Forming Reactions

4.1 Reduction versus Ring-Opening Polymerization of Cyclic Ethers

4.2 Polymerization versus Rearrangement of Vinyl Ethers

4.3 Is ‘R₃Si⁺’ Involved in the Reactions?

4.4 Applications of ‘R₃Si⁺’-Mediated Reactions

5 Reductions with Unique Selectivity

6 Surfing the Periodic Table

7 Concluding Remarks

Key words

homogeneous catalysis, reduction, hydrosilylation, amides, carboxylic acids, esters, metal complexes

• References

• 1a Smith MB, March J In March’s Advanced Organic Chemistry . 6th Ed. Wiley Interscience; Hoboken: 2007. Chap. 9, 1786-1869
• 1b Modern Reduction Methods . Andersson PG, Munslow IJ. Wiley-VCH; Weinheim: 2008
• 2a Nishimura S In Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis . John Wiley & Sons; New York: 2001. Chap. 5–10, 170–41
• 2b Augustine RL. Heterogeneous Catalysis for the Synthetic Chemist . Marcel Dekker; New York: 1996. Chap. 18, 439-472
• 3a Brunner H In Applied Homogeneous Catalysis with Organometallic Compounds . 2^nd Ed., Cornils B, Herrmann WA. Wiley-VCH; Weinheim: 2002. Chapter 2.2, 195-212
• 3b Chaloner PA, Esteruelas MA, Joó F, Oro LA. Homogeneous Hydrogenation . Springer; Netherland: 2010
• 3c Noyori R. Angew. Chem. Int. Ed. 2002; 41: 2008
• 4a Seyden-Penne J. Reduction by the Alumino- and Borohydrides in Organic Synthesis, 2^nd Ed. Wiley-VCH; 1997
• 4b Hajós A. Complex Hydrides . Elsevier; Amsterdam: 1979
• 5 Larson GL, Fry JL. Ionic and Organometallic-Catalyzed Organosilane Reductions . John Wiley & Sons,; 2010
• 6a For a review, see: Kursanov DN, Parnes ZN, Loim NM. Synthesis 1974; 633
• 6b West CT, Donnelly SJ, Kooistra DA, Doyle MP. J. Org. Chem. 1973; 38: 2675
• 6c Fry JL, Orfanopoulos M, Adington MG, Ditterman JrW, Silverman SB. J. Org. Chem. 1978; 43: 374
• 6d Mayr H, Dogan B. Tetrahedron Lett. 1997; 38: 1013
• 7a Fujita M, Hiyama T. J. Am. Chem. Soc. 1984; 106: 4629
• 7b Corriu RJ. P, Perz R, Reye C. Tetrahedron 1983; 39: 999
• 7c Chuit C, Corriu RJ. P, Perz R, Reye C. Synthesis 1982; 981
• 8a Marciniec B In Hydrosilylation . Marciniec B. Springer; 2009. Chap. 9–10, 289–398
• 8b Comprehensive Handbook on Hydrosilylation. Marciniec B. Pergamon Press; Oxford: 1992. Chap. 3, 139-154
• 8c Ojima I In The Chemistry of Organicsilicon Compounds. Vol. 1, Chap. 25. Patai S, Rappoport Z. Wiley; Chichester: 1989: 1479-1526
• 8d Ojima I, Li Z, Zhu J In The Chemistry of Organic Silicon Compounds. Vol. 2, Chap. 29. Patai S, Rappoport Z. Wiley; Chichester: 1998: 1687-1792
• 8e Carpentier J.-F, Bett V. Curr. Org. Chem. 2002; 6: 913-936
• 8f Nishiyama H In Transition Metals for Organic Synthesis. Vol. 2, 2nd Ed. Beller M, Bolm C. Wiley-VCH; Weinheim: 2004: 182-191
• 8g Rendler S, Oestreich M. Angew. Chem. Int. Ed. 2007; 46: 498
• 8h Díez-González S, Nolan SP. Acc. Chem. Res. 2008; 41: 349
• 8i Enthaler S. ACS Catal. 2013; 3: 150
• 9 Addis D, Das S, Junge K, Beller M. Angew. Chem. Int. Ed. 2011; 50: 6004
• 10a Berk SC, Kreutzer KA, Buchwald SL. J. Am. Chem. Soc. 1991; 113: 5093
• 10b Barr KJ, Berk SC, Buchwald SL. J. Org. Chem. 1994; 59: 4323
• 10c Reding MT, Buchwald SL. J. Org. Chem. 1995; 60: 7884
• 10d Verdaguer X, Berk SE, Buchwald SL. J. Am. Chem. Soc. 1995; 117: 12641
• 10e Verdaguer X, Hansen MC, Berk SC, Buchwald SL. J. Org. Chem. 1997; 62: 8522
• 11 Mao Z, Gregg BT, Cutler AR. J. Am. Chem. Soc. 1995; 117: 10139
• 12 Mimoun H. J. Org. Chem. 1999; 64: 2582
• 13a Kuwano R, Takahashi M, Ito Y. Tetrahedron Lett. 1998; 39: 1017
• 13b Igarashi M, Fuchikami T. Tetrahedron Lett. 2001; 42: 1945
• 13c Igarashi M, Mizuno R, Fuchikami T. Tetrahedron Lett. 2001; 42: 2149
• 13d Ohta T, Kamiya M, Nobutomo M, Kusui K, Furukawa I. Bull. Chem. Soc. Jpn. 2005; 78: 1856
• 14 For the hydrosilylation of nitriles: Murai T, Sakane T, Kato S. J. Org. Chem. 1990; 55: 449
• 15 Fernandes AC, Romão CC. J. Mol. Catal. A: Chemical 2007; 272: 60
• 16 Díez-González S, Scott NM, Nolan SP. Organometallics 2006; 25: 2355
• 17 Thayer A. Chem. Eng. News 2005; 83 ( 36) ,55
• 18 Committee for Medicinal Products for Human Use (CHMP), European Medicines Agency Guideline on the Specification Limits for Residues of MetalEMEA/CHMP/SWP/4446/2000, http://www.ema.europa.eu/ema/, 2008.
• 19 O’Connor JM, Casey CP. Chem. Rev. 1987; 87: 307
• 20a Nagashima H, Fukahori T, Aoki K, Itoh K. J. Am. Chem. Soc. 1993; 115: 10430
• 20b Nagashima H, Suzuki A, Nobata M, Itoh K. J. Am. Chem. Soc. 1996; 118: 687
• 21 Ojima I, Kogure T. Organometallics 1982; 1: 1390
• 22a Nagashima H, Tatebe K, Ishibashi T, Nakaoka A, Sakakibara J, Itoh K. Organometallics 1995; 14: 2868
• 22b Nagashima H, Tatebe K, Ishibashi T, Sakakibara J, Itoh K. Organometallics 1989; 8: 2495
• 22c The rate acceleration is accompanied by a unique 1,4-methyl group migration between two silicon atoms: Nagashima H, Tatebe K, Itoh K. J. Chem. Soc., Perkin Trans. I 1989; 1707
• 23a Nagashima H, Suzuki A, Iura T, Ryu K, Matsubara K. Organometallics 2000; 19: 3579
• 23b Matsubara K, Iura T, Maki T, Nagashima H. J. Org. Chem. 2002; 67: 4985
• 23c Motoyama Y, Itonaga C, Ishida T, Takasaki M, Nagashima H. Org. Synth. 2005; 82: 188
• 24 Hanada S, Ishida T, Motoyama Y, Nagashima H. J. Org. Chem. 2007; 72: 7551
• 25 Motoyama Y, Mitsui K, Ishida T, Nagashima H. J. Am. Chem. Soc. 2005; 127: 13150
• 26a Lawrence NJ, Drew MD, Bushell SM. J. Chem. Soc., Perkin Trans. 1 1999; 3381
• 26b Lavis JM, Maleszka RE. Jr In Handbook of Reagents for Organic Synthesis: Reagents for Silicon-Mediated Organic Synthesis . Fuchs PL. John Wiley & Sons Ltd; Chichester: 2011: 427

See for example:
• 27a Frainnet E, Esclamadon C. Compt. Rend. 1962; 254: 1814
• 27b Mori A, Ishihara K, Yamamoto H. Tetrahedron Lett. 1986; 27: 987
• 28 Ohta T, Michibata T, Yamada K, Omori R, Furukawa I. Chem. Commun. 2003; 1192
• 29a Park S, Brookhart M. Chem. Commun. 2011; 47: 3643
• 29b Gansäuer A, Klatte M, Brändle GM, Friedrich J. Angew. Chem. Int. Ed. 2012; 51: 8891
• 30a Matsubara K, Terasawa J, Nagashima H. J. Organomet. Chem. 2002; 660: 145
• 30b Harada N, Yasuhara J, Motoyama Y, Fujimura O, Tsuji T, Takahashi T, Takahashi Y, Nagashima H. Bull. Chem. Soc. Jpn. 2011; 84: 26
• 31a Cationic Polymerizations. Matyjaszewski K. Marcel Dekker; New York: 1996
• 31b Goethals EJ, Prez FD. Prog. Polym. Sci. 2007; 32: 220
• 32a For a review, see: Luzt RP. Chem. Rev. 1984; 84: 206
• 32b Palani N, Balasubramanian KK. Tetrahedron Lett. 1995; 52: 9527
• 32c Petasis NA, Lu S.-P. J. Am. Chem. Soc. 1995; 117: 6394
• 32d Smith AB. III, Verhoest PR, Minbiole KP, Lim JJ. Org. Lett. 1999; 1: 909
• 32e du Roizel B, Sollogoub M, Pearce AJ, Sinaÿ P. Chem. Commun. 2000; 1507
• 32f Gansäuer A, Fielenback D, Stock C, Geich-Gimbel D. Adv. Synth. Catal. 2003; 345: 1017
• 33a Nagashima H, Itonaga C, Yasuhara J, Motoyama Y, Matsubara K. Organometallics 2004; 23: 5779
• 33b Harada N, Nishikata T, Nagashima H. Tetrahedron 2012; 68: 3243
• 34a Chalk AJ. J. Chem. Soc., Chem. Commun. 1970; 847
• 34b Crivello JV, Bi D. J. Polym. Sci.: Part A: Polymer Chemistry 1993; 31: 3121
• 34c Crivello J, Rajaraman SK. Tetrahedron 1997; 53: 15167
• 35a Chalk AJ, Harrod JF. J. Am. Chem. Soc. 1967; 89: 1640
• 35b Baay YL, MacDiarmid AG. Inorg. Nucl. Chem. Lett. 1967; 3: 159
• 36 Moore EJ, Sullivan JM, Norton JR. J. Am. Chem. Soc. 1986; 108: 2257
• 37a Olah GA, Wang Q, Li X, Rasul G, Prakash GK. S. Macromolecules 1996; 29: 1857
• 37b Prakash GK. S, Bae C, Rasul G, Olah GA. J. Org. Chem. 2002; 67: 1297
• 38a Hrkach JS, Matyjaszewski K. Macromolecules 1990; 23: 4042
• 38b Cho CG, Feit BA, Webster OW. Macromolecules 1992; 25: 2081
• 39a Kira M, Hino T, Sakurai H. Chem. Lett. 1992; 555
• 39b Müther K, Oestreich M. Chem. Commun. 2011; 47: 334
• 40a Parks DJ, Piers WE. J. Am. Chem. Soc. 1996; 118: 9440
• 40b Parks DJ, Blackwell JM, Piers WE. J. Org. Chem. 2000; 65: 3090
• 40c Piers WE, Marwitz AJ. V, Mercier LG. Inorg. Chem. 2011; 50: 12252
• 41a Hog DT, Oestreich M. Eur. J. Org. Chem. 2009; 5047
• 41b Mewald M, Oestreich M. Chem.–Eur. J. 2012; 18: 14079
• 42a Yang J, White PS, Schauer CK, Brookhart M. Angew. Chem. Int. Ed. 2008; 47: 4141
• 42b Park S, Brookhart M. Organometallics 2010; 29: 6057
• 42c Park S, Brookhart M. J. Am. Chem. Soc. 2012; 134: 640
• 42d Cheng C, Brookhart M. J. Am. Chem. Soc. 2012; 134: 11304
• 42e Yang J, Brookhart M. Adv. Synth. Catal. 2009; 351: 175
• 42f Yang J, White PS, Brookhart M. J. Am. Chem. Soc. 2008; 130: 17509
• 43a Metsänen TT, Hrobárik P, Klare HF. T, Kaupp M, Oestreich M. J. Am. Chem. Soc. 2014; 136: 6912
• 43b Wang W, Gu P, Wang Y, Wei H. Organometallics 2014; 33: 847
• 44 Hanada S, Yuasa A, Kuroiwa H, Motoyama Y, Nagashima H. Eur. J. Org. Chem. 2010; 1021
• 45 Gevogyan V, Rubin M, Benson S, Liu J.-X, Yamamoto Y. J. Org. Chem. 2000; 65: 6179
• 46 Jung ME, Lyster MA. J. Org. Chem. 1977; 42: 3761
• 47 Nagashima H, Kubo Y, Kawamura M, Nishikata T, Motoyama Y. Tetrahedron 2011; 67: 7667
• 48 Nishikata T, Nagashima H. Angew. Chem. Int. Ed. 2012; 51: 5363
• 49 Augustine JK, Naik YA, Mandal AB, Alagarsamy P, Akabote V. Synlett 2008; 2429
• 50a For a review, see: Augé J, Lubin-Germain N, Uziel J. Synthesis 2007; 1739
• 50b Sakai N, Nagasawa K, Ikeda R, Nakaike Y, Konakahara T. Tetrahedron Lett. 2011; 52: 3133
• 50c Sakai N, Kawana K, Ikeda R, Nakaike Y, Konakahara T. Eur. J. Org. Chem. 2011; 3178
• 50d Inamoto Y, Kaga Y, Nishimoto Y, Yasuda M, Baba A. Org. Lett. 2013; 15: 3452
• 51 Lane CF. Chem. Rev. 1976; 76: 773
• 52a Sasakuma H, Motoyama Y, Nagashima H. Chem. Commun. 2007; 4916
• 52b Yumino S, Hashimoto T, Tahara A, Nagashima H. Chem. Lett. 2014; 43: 1829

For representative examples, see:
• 53a Brown HC, Krishnamurthy S. Tetrahedron 1979; 35: 567
• 53b Ward DE, Rhee CK. Can. J. Chem. 1989; 67: 1206
• 53c Kuroiwa Y, Matsumura S, Toshima K. Synlett 2008; 2523
• 53d Ranu BC. Synlett 1993; 885
• 53e Zeynizadeh B. Bull. Chem. Soc. Jpn. 2003; 76: 317
• 53f Krishnamurthy S. J. Org. Chem. 1981; 46: 4628
• 53g Brown HC, Kulkarni S. J. Org. Chem. 1977; 42: 4169

For example:
• 54a Fujiwara T, Cong C, Terao J, Tsuji Y. Adv. Synth. Catal. 2013; 355: 3420
• 54b Gooßen LJ, Ghosh K. Chem. Commun. 2002; 836
• 54c Izawa T, Mukaiyama T. Bull. Chem. Soc. Jpn. 1979; 52: 555
• 55a Chandrasekhar S, Kumar MS, Muralidhar B. Tetrahedron Lett. 1998; 39: 909
• 55b Brown HC, Cha JS, Yoon NM, Nazer B. J. Org. Chem. 1987; 52: 5400
• 55c Hubert TD, Eyman DP, Wiemer DF. J. Org. Chem. 1984; 49: 2279
• 55d Sato F, Jinbo T, Sato M. Synthesis 1981; 871
• 55e Muraki M, Mukaiyama T. Chem. Lett. 1974; 1447
• 56 Miyamoto K, Motoyama Y, Nagashima H. Chem. Lett. 2012; 41: 229

Recent examples for selective reduction of carboxylic acids with hydrosilanes, see:
• 57a Zheng J, Chevance S, Darcel C, Sortais J.-B. Chem. Commun. 2013; 49: 10010
• 57b Bézier D, Park S, Brookhart M. Org. Lett. 2013; 15: 496
• 57c Castro LC. M, Li H, Sortais J.-B, Darcel C. Chem. Commun. 2012; 48: 10514
• 58 In a related study, Fuchikami and Igarashi reported that hydrosilylation of esters with low activity catalysts resulted in silyl alkyl acetals, of which hydrolysis afforded the aldehydes.^13b See also: Li H, Castro LC. M, Zheng J, Roisnel T, Dorcet V, Sortais J.-B, Darcel C. Angew. Chem. Int. Ed. 2013; 52: 8045
• 59 Hanada S, Motoyama Y, Nagashima H. Eur. J. Org. Chem. 2008; 4097
• 60 Rigo B, Lespagnol C, Pauly M. Tetrahedron Lett. 1986; 27: 347
• 61a Calas R, Frainnet E, Bazouin A. Compt. Rend. 1962; 254: 2357
• 61b Zhou S, Addis D, Shoubhik D, Junge K, Beller M. Chem. Commun. 2009; 4883
• 62a Hanada S, Motoyama Y, Nagashima H. Tetrahedron Lett. 2006; 47: 6173
• 62b Hanada S, Tsutsumi E, Motoyama Y, Nagashima H. J. Am. Chem. Soc. 2009; 131: 15032
• 63a Cullen WR, Evans SV, Han NF, Trotter J. Inorg. Chem. 1987; 26: 514
• 63b Hayashi T, Yamamoto K, Kumada M. J. Organomet. Chem. 1976; 112: 253
• 64a Motoyama Y, Aoki M, Takaoka N, Aoto R, Nagashima H. Chem. Commun. 2009; 1574
• 64b Tahara A., Miyamoto Y., Aoto R., Motoyama Y., Sunada Y., Nagashima H.; submitted for publication.
• 65 Corriu RJ. P, Moreau JJ. E, Pataud-Sat M. J. Organomet. Chem. 1982; 228: 301
• 66a Enamines: Synthesis, Structure and Reactions. 2nd Ed; Cook AG. Marcel Dekker; New York: 1992
• 66b Bélanger G, Doré M, Ménard F, Darsigny V. J. Org. Chem. 2006; 71: 7481 ; and references cited therein
• 67a Sinicropi JA, Cowdery-Corvan JR, Magin EH, Borsenberger PM. Chem. Phys. 1997; 218: 331
• 67b Paspirgelyte R, Grazulevicius JV, Grigalevicius S, Jankauskas V. Synth. Metal. 2009; 159: 1014 ; and references cited therein
• 68 Nagashima H, Sunada Y, Nishikata T, Chaiyanurakkul A. Iron-Promoted Reduction Reactions In The Chemistry of Organoiron Compounds. Malek I, Rappoport Z. Wiley; Chichester, UK: 2014. Chap 9, 325-378
• 69a Bullock RM. Angew. Chem. Int. Ed. 2007; 46: 7360
• 69b Gaillard S, Renaud J.-L. ChemSusChem 2008; 1: 505
• 69c Junge K, Schroder K, Beller M. Chem. Commun. 2011; 47: 4849
• 69d Le Bailly BA. F, Thomas SP. RSC Adv. 2011; 1: 1435

For representative reports, see:
• 70a Brunner H, Fisch K. Angew. Chem., Int. Ed. Engl. 1990; 29: 1131
• 70b Nishiyama H, Furuta A. Chem. Commun. 2007; 760
• 70c Shaikh NS, Enthaler S, Junge K, Beller M. Angew. Chem., Int. Ed. 2008; 47: 2497
• 70d Langlotz BK, Wadepohl H, Gade LH. Angew. Chem. Int. Ed. 2008; 47: 4670
• 70e Tondreau AM, Darmon JM, Wile BM, Floyd SK, Lobkovsky E, Chirik PJ. Organometallics 2009; 28: 3928
• 70f Yang J, Tilley TD. Angew. Chem. Int. Ed. 2010; 49: 10186

See also the following papers and references cited therein:
• 70g Ruddy AJ, Kelly CM, Crawford SM, Wheaton CA, Sydora OL, Small BL, Stradiotto M, Turculet L. Organometallics 2013; 32: 5581
• 70h Volkov A, Buitrago E, Adolfsson H. Eur. J. Org. Chem. 2013; 2066
• 70i Zhao H, Sun H, Li X. Organometallics 2014; 33: 3535
• 71a Sunada Y, Kawakami H, Imaoka T, Motoyama Y, Nagashima H. Angew. Chem. Int. Ed. 2009; 48: 9511
• 71b Zhou S, Junge KD, Addis D, Das S, Beller M. Angew. Chem. Int. Ed. 2009; 48: 9507
• 72a Zhou S, Addis D, Das S, Junge K, Beller M. Chem. Commun. 2009; 4883
• 72b Junge K, Wendt B, Zhou S, Beller M. Eur. J. Org. Chem. 2013; 2061
• 72c Das S, Li Y, Junge K, Beller M. Chem. Commun. 2012; 48: 10742
• 72d Das S, Wendt B, Möller K, Junge K, Beller M. Angew. Chem. Int. Ed. 2012; 51: 1662
• 73a Tsutsumi H, Sunada Y, Nagashima H. Chem. Commun. 2011; 47: 6581
• 73b Sunada Y, Tsutsumi H, Shigeta K, Yoshida R, Hashimoto T, Nagashima H. Dalton Trans. 2013; 42: 16687
• 74a Hosokawa S, Ito J, Nishiyama H. Organometallics 2010; 29: 5773
• 74b Castro LC. M, Sortais J.-B, Darcel C. Chem. Commun. 2012; 48: 151
• 74c Blom B, Tan G, Enthaler S, Inoue S, Epping JD, Driess M. J. Am. Chem. Soc. 2013; 135: 18108
• 74d Zuo Z, Sun H, Wang L, Li X. Dalton Trans. 2014; 43: 11716
• 75 An improved preparative method of 1 was investigated by using the less expensive acenaphthylene containing acenaphthene (>80% purity Tokyo Kasei Co. Ltd.). Chromatographic purification of 1 at the final step was replaced by crystallization. From 15.8 g of RuCl₃·3H₂O, 9.5 g of 5 was obtained by the two-step procedure described below. A solution of RuCl₃·3H₂O (60.8 mmol, 15.8 g) dissolved in MeOH (390 mL) was placed in a stainless autoclave (2 L), and the atmosphere was replaced by CO. The autoclave was heated at 130 °C without stirring for 24 h. The reactor was cooled to room temperature, and the pressure was carefully released. The precipitated orange crystals of Ru₃(CO)₁₂ were collected by filtration, washed with methanol, and dried in vacuum (10.0 g, 77% yield). In a three-neck flask fitted with a reflux condenser were placed Ru₃(CO)₁₂ (10.0 g, 15.7 mmol) acenaphthylene (80% purity, 18.78 mmol, 2.95 g, 1.2 equiv), and heptane (1.1 L). The mixture was heated at 120 °C for 48 h under an argon atmosphere. After cooling, the formed solid was separated by filtration, and it was washed with hexane (150 mL) until the washings became colorless. A ¹H NMR spectrum of the solid confirmed that all of the acenaphthylene and acenaphthene was washed out. The crude solid of 1 (9.73 g) was dissolved in CH₂Cl₂ (490 mL), and hexane (1.2 L) was slowly added to the solution. Orange microcrystals of 1 (8.58 g, 84%) precipitated from the solution. The mother liquor was concentrated and the formed solid was subjected to recrystallization in a similar manner as above to give an additional 0.91 g of 1.
• 76a Reeves JT, Tan Z, Marsini MA, Han ZS, Xu Y, Reeves DC, Lee H, Lu BZ, Senanayake CH. Adv. Synth. Catal. 2013; 355: 47 . See also
• 76b Gutsulyak DV, Nikonov GI. Angew. Chem. Int. Ed. 2010; 49: 7553
• 77a Revunova K, Nikonov GI. Chem.–Eur. J. 2014; 20: 839
• 77b Fernández-Salas JA, Manzini S, Nolan SP. Chem. Commun. 2013; 49: 9758
• 77c Manas MG, Sharninghausen LS, Balcells D, Crabtree RH. New J. Chem. 2014; 38: 1694
• 78 We compared the catalyst activity of 1 with Ru₃(CO)₁₂ at low catalyst loadings (0.15 mol% with respect to the substrate). The reduction of N,N-dimethyl-p-methoxybenzamide with PhMe₂SiH (4.4 equiv with respect to the amide) in the presence of 1 was complete after 6 hours (TON = 666, TOF (h^–1) = 111) at room temperature (ca. 20 °C). Under the same conditions, Ru₃(CO)₁₂ was deactivated after 25% conversion of the amide. The catalyst showing highest catalytic activity was a ruthenium homologue of Sunada’s iron complex (Scheme 28); the reaction was over within 2 hours under the conditions (TON = 666, TOF (h^–1) = 334); Sunada Y., Inoue R., Nagashima H. to be submitted.

For recent examples of hydrosilane reduction of carboxylic acid derivatives with other base metal catalysts, see:
• 79a Mn: Zheng J, Chevance S, Darcel C, Sortais J.-B. Chem. Commun. 2013; 49: 10010
• 79b Co: Dombray T, Heleu C, Darcel C, Sortais J.-B. Adv. Synth. Catal. 2013; 355: 3358
• 79c Re: Toh CK, Sum YN, Fong WK, Ang SG, Fan WY. Organometallics 2012; 31: 3880
• 79d Mo: Arias-Ugarte R, Sharma HK, Morris AL. C, Pannell KH. J. Am. Chem. Soc. 2012; 134: 848
• 79e Zn: Das S, Addis D, Zhou S, Junge K, Beller M. J. Am. Chem. Soc. 2010; 132: 1770
• 80a Motoyama Y, Abe M, Kamo K, Kosako Y, Nagashima H. Chem. Commun. 2008; 44: 5321
• 80b Motoyama Y, Kamo K, Nagashima H. Org. Lett. 2009; 11: 1345
• 80c Motoyama Y, Kamo K, Yuasa A, Nagashima H. Chem. Commun. 2010; 46: 2256
• 80d Motoyama Y, Nishikata T, Nagashima H. Chem. Asian J. 2011; 6: 78
• 81a Vankelecom IF. J, Tas D, Parton RF, Van de Vyver V, Jacobs PA. Angew. Chem., Int. Ed. Engl. 1996; 35: 1346
• 81b Wolfson A, Janssens S, Vankelecom I, Geresh S, Gottlieb M, Herskowitz M. Chem. Commun. 2002; 388
• 81c Mwangi MT, Runge MB, Bowden NB. J. Am. Chem. Soc. 2006; 128: 14434 (82)
• 81d Matsubara K, Ryu K, Maki T, Iura T, Nagashima H. Organometallics 2002; 21: 3023
• 82a Sunada Y, Fujimura Y, Nagashima H. Organometallics 2008; 27: 3502
• 82b Tsutsumi H, Sunada Y, Nagashima H. Organometallics 2011; 30: 68

For related disilametallacylic iron and ruthenium complexes, see:
• 83a Sunada Y, Imaoka T, Nagashima H. Organometallics 2013; 32: 2112
• 83b Sunada Y, Imaoka T, Nagashima H. Organometallics 2010; 29: 6157

Recently, the proximity effect in the platinum-catalyzed hydrosilylation of amides was discussed in the following two papers. Beller and co-workers did not observe a rate enhancement by TMDS in the reaction using (diene)Pt(NHC). Pannel confirmed the monofunctionalization of TMDS in the reaction with DMF by Karstedt’s catalyst, which was similar to the RhCl(PPh₃)₃-catalyzed monofunctionalization of Me₂HSi(CH₂)_nSiHMe₂ (n = 2 or 3) with acetone in our previous work.²² We are now investigating them using DFT calculations.⁸⁵ See:
• 84a Piseiwicz S, Junge K, Beller M. Eur. J. Org. Chem. 2014; 2345
• 84b Martinez JL, Sharma HK, Arias-Ugarte R, Pannell KH. Organometallics 2014; 33: 2964
• 85 Nakatani N., Hasegawa J., Sunada Y., Nagashima H. submitted for publication.
• 86a Tilley TD, Glaser PB. J. Am. Chem. Soc. 2003; 125: 13640
• 86b Gutsulyak DV, Vyboishchikov SF, Nikonov GI. J. Am. Chem. Soc. 2010; 132: 5950
• 86c Nolin KA, Krumper JR, Pluth MD, Bergman RG, Toste FD. J. Am. Chem. Soc. 2007; 129: 14684
• 86d Shirobokov OG, Kuzmina LG, Nikonov GI. J. Am. Chem. Soc. 2011; 133: 6487

For theoretical studies on hydrosilylation reactions, see:
• 87a Sakaki S, Mizoe N, Sugimogo M, Musashi Y. Coord. Chem. Rev. 1999; 190–192: 933
• 87b Beddie C, Hall MB. J. Am. Chem. Soc. 2004; 126: 13564
• 87c Drees M, Strassner T. Inorg. Chem. 2007; 46: 10850
• 87d Wang W, Gu P, Wang Y, Wei H. Organometallics 2014; 33: 847
• 87e Yang Y.-F, Chung LW, Zhang X, Houk KN, Wu Y.-D. J. Org. Chem. 2014; 79: 8856 ; and references cited therein
• 88a Zhang J, Leitus G, Ben-David Y, Milstein D. Angew. Chem. Int. Ed. 2006; 45: 1113
• 88b Gunanathan C, Milstein D. Acc. Chem. Res. 2011; 44: 588
• 88c Zell T, Ben-David Y, Milstein D. Angew. Chem. Int. Ed. 2014; 53: 4685

See also:
• 89a Dub PA, Ikariya T. ACS Catal. 2012; 2: 1718
• 89b Coetzee J, Dodds DL, Klankermayer J, Brosinski S, Leitner W, Slawin AM. Z, Cole-Hamilton DJ. Chem.–Eur. J. 2013; 19: 11039 ; and references cited therein