Transition Metal-Catalyzed Hydro-, Sila-, and Stannastannation of Cyclopropenes: Stereo- and Regioselective Approach toward Multisubstituted Cyclopropyl Synthons Marina Rubina, Michael Rubin, and Vladimir Gevorgyan* Department of Chemistry, UniVersity of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061 Received May 29, 2002 Cyclopropylstannanes, highly attractive versatile synthons, are extensively used nowadays as stable precursors for a number of cyclopropylmetal reagents with defined configurations. 1 Further- more, they are employed in Pd-catalyzed oxidative homocoupling, 2 Stille cross-coupling reactions, 3 as well as in various destannylative transformations 4 and rearrangements into other useful organotin derivatives. 5 Although more than a few methods for the preparation of cyclopropylstannanes have been developed, 6 usually these methods lack generality and, in most cases, are limited to the preparation of mono- to trisubstituted cyclopropanes. A direct hydrostannation 7 of the cyclopropene double bond potentially can be seen as a very attractive, straightforward, and atom-economic alternative route to highly substituted cyclopropylstannanes. The 54 kcal/mol of strain energy in cyclopropene versus cyclopropane is a reason for the high affinity of its double bond toward various addition reactions. 8 However, transition metal-catalyzed hydrostan- nation of cyclopropenes has never been reported, probably because of a general belief that, except for some scattered reports, 9 palladium, as well as some other transition metal complexes, is well known to cause ring-opening, 10 oligomerization, 11 or poly- merization 12 of cyclopropenes. 13 Herein we wish to report the first highly stereo- and regioselective transition metal-catalyzed hydro-, sila-, and stannastannation reactions of cyclopropenes 14 which allow for the synthesis of up to pentasubstituted cyclopropane derivatives in very good yields. Initially, we tested hydrostannation of disubstituted cyclopropene 1a 15 in the presence of a number of transition metal catalysts (eq 1, Table 1). The ruthenium, platinum, rhodium, and nickel complexes tested initiated rather slow reactions which produced moderate to good yields of products albeit with high facial selectivity (Table 1, entries 1-4). Most of the Pd-catalysts showed high reaction rates, but yields and selectivity were disappointingly * To whom correspondence should be addressed. E-mail: vlad@uic.edu. Table 1. Catalyst Optimization for Hydrostannation of 1a # catalyst time 3,% a 4,% a 3:4 a 1 Ru(PPh3)3Cl2 20 h 67 3 96:4 2 Pt(PPh3)4 20 h 66 4 94:6 3 Rh(PPh3)3Cl 20 h 75 4 95:5 4 Ni(dppp)Cl2 20 h 32 1 97:3 5 Ni(dppe)2 5h 2 6 Pd(PPh3)2Cl2 5 min 36 16 69:31 7 TCPC b 5 min 15 14 52:48 8 Pd(OAc)2/TDMPP 5 min 19 15 56:44 9 Pd2dba3/o-Tol3P 5 min >1 10 [π-allyl-PdCl]2/MOP 5 min 29 6 83:17 11 [π-allyl-PdCl]2/MOP b 5 min 32 8 80:20 12 Pd(PPh3)4 5 min 79 >1 98:2 13 Pd(PPh3)4 c 5 min 86 d >1 >99:1 14 none 5 min 20 24 46:54 a GC data. b TCPC ) [1,2,3,4-tetrakis(methoxycarbonyl)-1,3-butadiene- 1,4-diyl]palladium. c Reaction was performed at -78 °C. d Isolated yield. Table 2. Pd-Catalyzed Hydrostannation of Cyclopropenes a Isolated yield. b Formation of 5% of 4ab was detected. c Combined yield of 4:1 mixture of 3ea:4ea. d Combined NMR yield of 4:1 mixture of 3fa:4fa. e NMR yield. f Formation of 5% of 4ha was observed. Published on Web 09/10/2002 11566 9 J. AM. CHEM. SOC. 2002, 124, 11566-11567 10.1021/ja027095k CCC: $22.00 © 2002 American Chemical Society