MIDA–Vinylsilanes: Selective Cross-Couplings and Applications to the Synthesis of Functionalized Stilbenes

Abstract

A rapid and stereodefined synthesis of MIDA-boryl vinylsilanes has been achieved through the hydrosilylation of an alkynylboronic ester. The E products which contain a silyl and boryl group can be selectively cross-coupled in a two-step bidirectional sequence to provide a rapid and high-yielding synthesis of complex styrenes.

Stereoselective Direct Chlorination of Alkenyl MIDA Boronates: Divergent Synthesis of E and Z α‐Chloroalkenyl Boronates

“…[18] As such, the retention of the CÀBb ond in the product demonstrates amajor advantage of our approach. [21] This is illustrated in Scheme 1e:u nder slow-release reaction conditions,S uzuki-Miyaura coupling of 2a with iodide 9 provided the alkenyl chloride 10 in 76 %y ield. [3g] Coppermediated Chan-Lam-type oxidative cyanation gave a-chloroalkenyl cyanide 6 in good efficiency (Scheme 1b).…”

“…[20] Thep resence of both C À B(MIDA) and C À Cl bonds in the product render it an ideal synthon for chemoselective iterative coupling reactions. [21] This is illustrated in Scheme 1e:u nder slow-release reaction conditions,S uzuki-Miyaura coupling of 2a with iodide 9 provided the alkenyl chloride 10 in 76 %y ield. [22] Subsequent Kumada coupling provided the tri-substituted alkene 11 (63 %y ield), which is akey intermediate for the synthesis of the antiestrogen agent Clomiphene· [23] On the other hand, Kumada coupling of 3a with (4-methoxyphenyl)magnesiumb romide led to the formation of the diarylated boryl-retentive alkene 12,a lthough in low yield (Scheme 1f).…”

Light‐Induced Gold‐Catalyzed Hiyama Arylation: A Coupling Access to Biarylboronates

“…This would enable a simple site-selective arylation of aryl compounds bearing both silyl and boronic ester derivatives giving rise to privileged biarylboronate building blocks in an orthogonal manner to common methodologies. In palladium catalysis substrates carrying both, boron and silicon substituents undergo a transmetalation of the boronic ester, [13,14] thus needing at least two more steps for the conversion of the resulting arylsilane products into arylboronates.…”

A Regio‐ and Stereodivergent Synthesis of Homoallylic Amines by a One‐Pot Cooperative‐Catalysis‐Based Allylic Alkylation/Hofmann Rearrangement Strategy

“…[30] Finally,t he preparation of an a,b-unsaturated ester substituted homobenzylic amine 27 was possible using a2-naphthylic phenylphosphate electro-phile in combination with XantphosPd G3. To address this limitation, benzyldimethylsilyl-substituted carbamate 29 was directly elaborated in diverse fashion by Pd-catalyzed Hiyama cross-couplings [31,32] with ar ange of (hetero)aryl and alkenyl iodides without erosion of enantioenrichment (Scheme 2; 30-35); ketone-(32), indole-(33), pyridine- (34), and dienoate-containing (35)products are all accessible from ac ommon intermediate (29). To address this limitation, benzyldimethylsilyl-substituted carbamate 29 was directly elaborated in diverse fashion by Pd-catalyzed Hiyama cross-couplings [31,32] with ar ange of (hetero)aryl and alkenyl iodides without erosion of enantioenrichment (Scheme 2; 30-35); ketone-(32), indole-(33), pyridine- (34), and dienoate-containing (35)products are all accessible from ac ommon intermediate (29).…”