Cyclopropyl- and Cyclobutylboronates and -silanes: A Stereo­selective Approach

Abstract

Chiral cyclopropyl- and cyclobutylboronic esters and -silanes have become attractive intermediates for the preparation of functionalized small rings. This review highlights the stereoselective methods developed for their preparation, including both diastereo- and enantio­selective approaches.1 Introduction2 Stereoselective Synthesis of Cyclopropyl- and Cyclobutylboronates and -silanes2.1 Diastereoselective Synthesis of Cyclopropyl- and Cyclobutylboronates and -silanes2.2 Asymmetric Synthesis of Cyclopropyl- and Cyclobutylboronates and -silanes3 Conclusions

Rapid Access to Chiral Spiro[2.3] Lactams: Stereoselective Hydroborylation and Hydrosilylation and Remote Control of Axial Chirality by Copper-Catalyzed Desymmetrization of Spirocyclopropenes

“…Recently, the desymmetrization strategy has been well developed and widely employed in asymmetric synthesis . For example, the diastereoselective and enantioselective hydroborylation and hydrosilylation of strained alkenes, including cyclopropenes , and cyclobutenes, , had been well established . Thus, the provided enantio-enriched boronic esters work as valuable synthetic building blocks, while the asymmetric hydrosilylation ranks as one of the most important reactions in organosilicon chemistry .…”

Regioselective 1,2-Alkylboration of Benzylidenecyclopropanes: Access to Csp3-Enriched Cyclopropyl Boronic Esters

“…Alongside a steep escalation in the utilization of boronic acid (ester) in the recent practice of drug development, organoboronic acid and its derivatives have received everlasting, vast prominence as carbon nucleophiles and radical progenitors in C–C/C-X bond-forming transformations, which hinge upon their innate reactivity, stability, and easy handling . Hence, considering all these alluring facets, Csp 3 -enriched cyclopropyl boronic acid derivatives constitute a promising advanced synthetic intermediate where boronic ester serves as synthetic handle for additional structural modification. , In this regime, a substantial advancement could be achieved for cyclopropylboronic esters; however, the sketched scaffold of complex Csp 3 -enriched cyclopropyl boronic ester seemingly has limited access, including (a) stoichiometric base-mediated cyclization of bis­(boryl) alkyl electrophiles ,, and (b) catalytic hydroboration of cyclopropenes (Scheme ). , …”

Copper catalyzed diastereoselective and enantioselective hydroborylation of cyclopentenylcarboxyesters

“…This discrepancy is even more remarkable, given that the diastereoselective and enantioselective hydroborylations of cyclopropene and cyclobutene derivatives have been widely reported. 9,10 It is worth mentioning that the diastereoselectivity control might benefit from the rigid backbones of small rings such as cyclopropene and cyclobutene, while relatively flexible 5-membered rings could be more challenging.…”

“…Inspired by the stereoselective hydroborylation of cyclopropenylcarboxyesters and cyclobutenylcarboxyesters, 9,10 we would like to develop a general, complementary approach to access optically-enriched boronyl-cyclopentylcarboxyesters. Here we disclose an efficient, clean and operationally simple method to access an array of optically-enriched boronyl cyclopentylcarboxyester derivatives, by using a copper catalyzed stereoselective hydroborylation.…”