Diastereoselective cyclopropanation of an allylic alcohol with a gem-dizinc carbenoid followed by an unusual zinc-boron exchange and further treatment with excess KHF 2 afforded 1,2,3-syncis-substituted cyclopropyl trifluoroborates in 58-63% overall yields. The potassium cyclopropyl trifluoroborates underwent Suzuki-Miyaura cross-coupling reactions to give 1,2,3-functionalized cyclopropanes in good yields. Finally, an oxidation-epimerization sequence gave access to 1,2,3-trans-substituted cyclopropyl trifluoroborate.Cyclopropylboron moieties have received increasing attention since they serve as good building blocks for cyclopropane chemistry. So far, synthetic applications have been focused on Suzuki-Miyaura cross-coupling reactions 1 and oxidation into cyclopropanols. 2 The rhodium-catalyzed hydroboration of cyclopropenes 3 is one method to generate optically active cyclopropylboron intermediates along with the direct cyclopropanation of vinylboronates. 1c,g,2a,b,4 Despite the fact that 1,2,3-substituted cyclopropanes are widely found in natural products and other biologically active molecules, 5 there are only three methods for their formation. 4a-c,6 Two of them are based on the cyclopropanation on the vinylboronate involving the preparation of substituted diazo derivatives. Alternate methods to generate 1,2,3-substituted cyclopropylboron species are highly desirable, and, we present herein a new method via an unusual zinc-boron exchange. Our group has recently developed a methodology for the synthesis of 1,2,3-substituted cyclopropylzinc based on cyclopropanation using gem-dizinc carbenoid 2. After quenching with different electrophiles, 1,2,3-functionalized cyclopropanes were produced (Scheme 1). 7Based on an intermediate 1,2,3-substituted cyclopropylzinc in this reaction, we wondered if it would be possible to generate a 1,2,3-substituted cyclopropylboron reagent by quenching with an electrophilic boron source, such as trimethylborate. Preliminary studies with alkene 1a and B(OMe) 3 as the electrophile gave a major product that we assigned as 7a, in addition to a significant amount of 6a (reduced product of a cyclopropylzinc). Unfortunately, the former could not be cleanly isolated from the crude reaction mixture.Organotrifluoroborates, which are readily prepared from organoboron intermediates and KHF 2 , 8 were shown to be readily isolable and stable compounds. These compounds are indefinitely stable in air and are sometimes more reactive than corresponding boronic esters or acids. They are used in various transformations, in particular palladiumcatalyzed cross-coupling reactions. 9 In order to isolate the cyclopropylboron species, we treated the crude reaction mixture with an excess of KHF 2 in methanol-water and we were able to isolate the pure 1,2,3-syn-cis-substituted potassium cyclopropyl trifluoroborate 8a in 50% overall yield, 10,11 confirming that we had indeed a cyclopropylboron moiety. Moreover, the zinc-boron exchange was done with a retention of configuration, as confirmed by 2D NOESY experim...