Synthesis of Asymmetrical‐Terminally Bifunctionlized Alkanes by Sequential Suzuki–Miyaura Coupling Using B‐Thexylboracyclanes

Abstract

A one‐pot, sequential Suzuki–Miyaura coupling (SMC) using B‐thexylboracyclanes is reported. We focused on a boracyclane with a bulky B‐substituent as an equivalent of a terminal heterobibora‐functionalized spacer. The first SMC of the boracyclane proceeded by endocyclic B–C bond cleavage due to the steric hindrance of the exocyclic B‐substituent to provide borinic acids. These subsequently underwent the second SMC under harsher conditions by transfer of the less hindered primary alkyl group to provide the asymmetrically bifunctionalized alkyl chain. The seven‐ to five‐membered boracyclanes were adaptable to the sequential SMC reactions to provide terminally bifunctional alkanes, although the efficiency of the transformation of the five‐membered boracyclane was poorer than those of the others. To demonstrate the utility of the method, we successfully prepared several terminally heterobifunctional hexanes in a one‐pot reaction.

Synthesis and Biological Evaluation of O‐Methylated Glycolipids Related to PGLs via Direct Stereoselective Glycosidation and Sequential Suzuki–Miyaura Coupling using Boracyclane

“…The fluorescent‐labelled glycosides 3 a – cB were used as chemical probes for the identification and detection of target proteins. The 4‐alkylphenyl glycosides 3 a – fA and 3 a – cB were prepared from the corresponding 4‐bromophenyl glycosides 4 a – f via sequential Suzuki–Miyaura palladium‐catalyzed cross‐coupling using boracyclane 5 and the aryl bromides 6A and 6B . Suzuki–Miyaura coupling of glycosides 4 a – f with boracyclane 5 provided the acyclic borinic acid 7 .…”

“…We further speculated that this method could involve a S N 2‐like substitution of in situ‐generated and unstable β‐glycosyl halides with glycosyl acceptors that could provide the 2‐deoxy‐α‐glycosides, which would make it adaptable to the direct synthesis of 2‐ O ‐methyl‐α‐glycosides. Herein, we report the preparation of PGL‐1 and PGL‐tb1 containing 4‐bromophenyl glycosides by direct α‐selective glycosidation of 2‐ O ‐methyl‐glycosyl imidates and modification of the glycosides by sequential Suzuki–Miyaura palladium‐catalyzed cross‐coupling using a boracyclane . In addition, we also evaluate the immunosuppressive activity of glycolipids.…”

“…Herein, we report the preparation of PGL-1 and PGL-tb1 containing 4-bromophenyl glycosides by direct a-selective glycosidation of 2-O-methyl-glycosyl imidates and modification of the glycosides by sequential Suzuki-Miyaura palladium-catalyzedc ross-cou-pling using ab oracyclane. [13] In addition, we also evaluate the immunosuppressive activity of glycolipids.…”

Developments in the Synthesis of Mycobacterial Phenolic Glycolipids

“…[68] As previously reported, these conditions could be used to install the desired α-rhamnosyl linkage with good stereoselectivity, in the absence of a C-2 neighboring group. [69] The assembled glycans were capped the with a parabromophenol on the reducing end which could be used for a sequential Suzuki-Miyaura coupling with boracyclane [70,71] to attach a hydrophobic anchor or fluorophore (Scheme 8). Direct coupling with brominated TokyoGreen® did not proceed well, possibly due to the lack of solubility and reduced reactivity of the deprotonated fluorophore.…”

Synthesis of Lignans Based on a Borate‐mediated One‐pot Sequential Suzuki‐Miyaura Coupling of Cyclic Boranes

“…Our group recently reported a one‐pot sequential Suzuki‐Miyaura coupling (SMC) [17] using the five‐, six‐, and seven‐membered cyclic boranes 8 possessing a sterically bulky B ‐substituent such as a thexyl group [18] to provide asymmetrically functionalized alkanes 9 (Scheme 1). [19] In this coupling, the cyclic boranes 8 were activated with a hydroxide ion to boronates 10 , followed by SMC to provide acyclic borinic acids 11 . Borinic acids 11 show low reactivity in SMC compared with boranes 8 and undergo further SMC with heating to provide alkanes 9 [20] .…”