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The insertion of the diazo derivative Me3SiCHN2 into pinB-SR σ bonds (R = Ph, Tol, Bn) allows a direct synthesis of multisubstituted H-C(SR)(Bpin)(SiMe3) compounds. Consecutive base-assisted transformations of HC(S)(B) (Si) systems lead to deborylative alkylations, Sommelet-Haüser rearrangements, and deprotoalkylations. Intramolecular cyclizations can be selectively performed either via desilylative or deborylative manifolds by fine-tuning the base employed.

This paper reports the first examples of Suzuki–Miyaura cross-couplings involving aryl- and naphthylphosphonate-based boronate esters as the nucleophilic partner. A systematic comparison of the performance of biaryl-like KITPHOS- and XPHOS-based systems revealed that, between them, an electronically and sterically diverse range of substrates can be coupled with remarkable efficiency to afford high yields of the corresponding biaryl and heterobiaryl monophosphonates. The use of an aryl- and naphthylphosphonate-based boronate ester as the coupling partner presents an alternative and potentially complementary pathway to existing couplings in which the aryl- or naphthylphosphonate unit is typically introduced as the electrophile. The potential advantages associated with the use of this new class of coupling partner were clearly demonstrated by the palladium-catalyzed reaction between diethyl [2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]phosphonate and 1-bromo-2-methoxynaphthalene that gave the corre...

Addition of o-C 6H 4NCHNAr to Rh(coe) 2(acac) (coe = cis-cyclooctene, acac = acetylacetonato) gave several new iminopyridine rhodium(I) complexes of the type Rh(acac)(kappa (2)- o-C 6H 4 NCH NAr) ( 1a Ar = 4-C 6H 4-OMe; 1b Ar = 2,6-C 6H 3-Me 2; 1c Ar = 2,6-C 6H 3-Et 2; 1d Ar = 2,6-C 6H 3- i-Pr 2). All new rhodium complexes have been characterized by a number of physical methods, including multinuclear NMR spectroscopy and X-ray diffraction studies for 1b and 1c. Addition of CHCl 3 to 1a afforded the corresponding rhodium(III) complex trans-Rh(kappa (2)- o-C 6H 4 NCH NAr)(CHCl 2)(Cl)(acac) ( 2). Addition of B 2cat 3 (cat = 1,2-O 2C 6H 4) to 1 gave zwitterionic Rh(eta (6)-catBcat)(kappa (2)- o-C 6H 4 NCH NAr) ( 3). The molecular structure of 3b has been confirmed by a single crystal X-ray diffraction study and shows that the N 2Rh fragment is bound to the catBcat anion via one of the catecholato groups in a eta (6)-fashion. These complexes have also been examined for their ability to catalyze the hydroboration of a series of vinylarenes. Reactions using catecholborane and pinacolborane seem to proceed largely through a dehydrogenative borylation mechanism to give a number of boronated products.

Reactions of tertiary phosphines or phosphinorhodium complexes with catecholborane (HB(cat)) give boron-substituent redistribution products. While sterically compact phosphines (PMe 3 , PEt 3 , PMe 2 Ph) react with 1 equiv of HBcat to give [(PR 3 ) 2 BH 2 ] + [B(cat) 2 ] - , bulkier phosphines (PPh 3 , PPr i 3 , PCy 3 ) afford phosphine-boranes H 3 B.PR 3 and tris(catecholato)diboron, B 2 (cat) 3 .

Addition of catecholborane to vinylarenes in the presence of Wilkinson's catalyst, [RhCl(PPh 3 ) 3 ], gives Markovnikov hydroboration products exclusively, whereas the corresponding reaction with α-substituted vinylarenes gives good yields of vinylboronate esters resulting from dehydrogenative borylation

α-Thioboronate esters are obtained directly in high yield and selectivity from metal-catalyzed additions of B−X bonds (X = H, B) to thiocarbonyl compounds and vinyl sulfides.

Multinuclear ( 1 H, 11 B, 13 C, 19 F, and 31 P) NMR spectroscopy was used to monitor primary products from transition metal-catalyzed addition of catecholborane (HBcat) to a variety of alkenes

Reactions of catecholborane (HBO 2 C 6 H 4 ) with RhCl(PPh 3 ) 3 (1) yield a variety of products depending on the B/Rh ratio, solvent, and temperature. Of particular relevance to catalyzed alkene hydroboration is degradation of HBO 2 C 6 H 4 to B 2 (O 2 C 6 H 4 ) 3 /«BH 3 » and the dihydride RhH 2 Cl(PPh 3 ) 3 (3). The molecular structure of 3, determined by X-ray diffraction, has meridional phosphine ligands and cis hydrides