Highly Diastereo- and Regioselective Transition Metal-Catalyzed Additions of Metal Hydrides and Bimetallic Species to Cyclopropenes:  Easy Access to Multisubstituted Cyclopropanes

Abstract

The first highly efficient, diastereo- and regioselective transition metal-catalyzed addition of metal hydrides (stannanes, silanes, and germanes) and bimetallic species (ditins and silyltins) to cyclopropenes has been developed. It was shown that the addition across the double bond of cyclopropenes is generally controlled by steric factors and proceeds from the least hindered face. This methodology represents a powerful and atom-economic approach toward a wide variety of highly substituted stereodefined cyclopropylmetals, useful building blocks unavailable by other methods.

Zinc‐Catalyzed Synthesis of Allylsilanes by Si−H Bond Insertion of Vinyl Carbenoids Generated from Cyclopropenes

“…Firstly, compared with precious metals typically employed in reactions of cyclopropenes involving carbene species (Au, Ru, Rh), inexpensive and low toxicity zinc salts showed superior efficiency. Besides, zinc catalysts exhibited complementary reactivity to PtCl 2 , which led to hydrosilylation products, as previously reported by Gevorgyan and coworkers …”

Cyclopropenylcarbinol Derivatives as New Versatile Intermediates in Organic Synthesis: Application to the Formation of Enantiomerically Pure Alkylidenecyclopropane Derivatives

“…Reduction of cyclopropenes (non-copper catalyzed) is reported in the literature for simple substrates, [31] and since diastereoselection in the hydrometalation of acyclic compounds is controlled by allylic, [21b, 32] homoallylic, [33] and even more remote stereogenic centers, [34] we thought that the diastereoselective reduction of cyclopropenylcarbinols 2 should be an interesting and powerful solution to the preparation of cyclopropylcarbinol derivatives 8 as described in Scheme 8. [35] We first reduced unsubstituted cyclopropenylcarbinols 2 j and 2 c (R 1 = H, R 2 = alkyl) with 1 equiv of LiAlH 4 in Et 2 O at + 40 8C. Under these conditions, we were pleased to obtain in good chemical yields the expected cyclopropylcarbinol products 8 a,b but with only a moderate anti selectivity (anti/syn 80:20) [36] as described in Table 7, entries 1 and 2.…”

Mechanistic Dichotomy of Magnesium‐ and Zinc‐Based Germanium Nucleophiles in the C(sp3)−Ge Cross‐Coupling with Alkyl Electrophiles

“…[1,2] Accordingly,there has been continuous interest in their synthesis,a nd several methods have already been described. [3][4][5][6] Of these,( transfer) hydrogermylation of alkenes is areliable option but usually limited to a-olefins to arrive at germanes substituted with linear alkyl chains; [3,4] electronically unbiased, internal alkenes usually give mixtures of regioisomeric a-branched alkyl-substituted germanes.A nother common approach is based on the nucleophilic substitution of alkyl halides and tosylates with lithium-based germanium nucleophiles (Scheme 1, top). [5] Theh igh reactivity of these hard germanium reagents is responsible for their poor functional-group tolerance and accounts for undesired side reactions.T he reverse approach, that is,n ucleophilic displacement at chlorogermanes with alkyl metal reagents,i sb urdened with the same incompatibility with functional groups and is even less general (Scheme 1, top).…”