Addition reactions or addition-carbocyclization reactions of a borylsilane with alkynes, a,w-diynes or an enyne compound proceed efficiently in the presence of palladium catalysts, P(OCH 2 ) 3 CEt being the ligand of choice.Addition reactions of inter-heteroatom bonds such as Si-Si and Sn-Sn to unsaturated carbon bonds are extremely useful for one-step generation of two heteroatom-carbon bonds. 1 Similar chemistry starting with B-B bonds is also rapidly emerging. 2 An obvious extension is addition reactions of bonds comprising two different elements. 3 In a previous paper we disclosed palladium-catalysed addition of borylstannanes to alkynes (borylstannylation) leading to efficient synthesis of 1-boryl-2-stannyl alkenes. 4 a,w-Diynes also react with borylstannanes, undergoing borylstannylative carbocyclization reactions to afford 1-borylmethylene-2-stannylmethylene cycloalkanes in high yields. 5a 1,4-Addition of conjugated dienes also proceeds smoothly when Pd(etpo) 2 catalyst [etpo = 4-ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane, P(OCH 2 ) 3 CEt] is used. 5b As regards corresponding borylsilylation, however, only unsuccessful results have been reported by Buynak and Geng. 6 While we were studying borylsilylation as a useful extension of the borylstannylation, Ito and co-workers briefly presented successful examples of addition reactions of a borylsilane (4,4,5,5-tetramethyl-2-dimethylphenylsilyl-2-bora-1,3-dioxapentane) to alkynes, mainly using the 1,1,3,3-tetramethylbutyl isocyanide-palladium diacetate catalyst system. 7 Their communication prompted us to report our own results.A representative procedure for the reaction of alkynes was as follows. A mixture of Pd 2 (dba) 3 (0.005 mmol; dba = dibenzylideneacetone) and etpo (0.02 mmol), i.e. Pd 2 (dba) 3 -etpo catalyst system in which P/Pd = 2, in C 6 D 6 (0.2 ml) was heated at 80 °C for 5 min, while the colour of the solution was changing from red to green. 1,3-Dimethyl-2-dimethylphenylsilyl-2-bora-1,3-diazacyclopentane 1 (0.2 mmol), oct-1-yne (0.3 mmol) and 1,4-dioxane (20 ml; internal standard for NMR analysis) were added to the resulting solution and the mixture was heated at 80 °C in a sealed NMR tube. NMR and GC-MS analyses of the reaction mixture after 2 h indicated complete consumption of 1 and adduct 2a † being formed in 92% yield (Scheme 1). Note that the regioselectivity was > 99% and that only a trace of isomer 2b was detected by NMR analysis. Isolation of the product was simple; evaporation of the reaction mixture, addition of hexane (2 ml) to the residue, filtration and distillation of the filtrate afforded nearly pure 2a in 84% isolated yield, which exhibited satisfactory spectral and analytical data. Observation of an 8% NOE between the allylic protons and the vinylic proton suggested that selective cis-addition of the B-Si bond had taken place.Unlike for the borylstannylation, Pd-PPh 3 complexes were not as efficient catalysts; the reaction of oct-1-yne with 1 did not proceed under the same conditions when either Pd(PPh 3 ) 4 or PdCl 2 (PPh ...

cis addition of the borylstannanes Me 3 SnB-[NMe(CH 2 CH 2 )NMe] (1) and Me 3 SnB(NEt 2 ) 2 (4) across alkynes was efficiently catalyzed at room temperature or 80 °C by Pd(PPh 3 ) 4 , Pd(dba) 2 , Cl 2 Pd(PPh 3 ) 2 , or Me 2 -Pd[PMe 2 (CH 2 CH 2 )PMe 2 ] to give (β-stannylalkenyl)boranes in high yields. Treatments of 1 with Me 2 Pd-[PMe 2 (CH 2 CH 2 )PMe 2 ] and of 4 with cis-Me 2 Pd(PPh 2 Me) 2 gave [{MeN(CH 2 CH 2 )MeN}B](Me 3 Sn)Pd[PMe 2 (CH 2 CH 2 )-PMe 2 ] (5) and [(Et 2 N) 2 B](Me 3 Sn)Pd(PPh 2 Me) 2 ( 6), respectively, with the former characterized by X-ray analysis. Complex 5, when treated with 1-octyne, formed the corresponding (β-stannyl-1-octen-1-yl)borane and could catalyze the addition reaction of 1 with 1-octyne.Transition-metal-catalyzed addition reactions of interheteroatom bonds such as Si-Si, 1 Sn-Sn, 1j, 2 Si-Sn, 3 and B-B 4 with unsaturated organic compounds have recently attracted increasing interest, since the resulting compounds are extremely useful as synthetic reagents and monomers for heteroatom-containing polymers. However, similar reactions of inter-heteroatom bonds for elements of two different groups are still very rare 5 except for "ate" complexes, 6 though the resulting

Highly regio- and stereoselective borylstannylative carbocyclization of diynes 2a − f with the borylstannane 1 are efficiently catalyzed at room temperature by a series of palladium complexes such as Cl2Pd(PPh3)2, Cl2Pd[P(o-tolyl)3]2, Pd(PPh3)4, and Pd(dba)2, giving 1-(borylmethylidene)-2-(stannylmethylidene)cycloalkane derivatives 3a − f in high yields. A 1,6-enyne (2g) also reacts similarly to afford a high yield of the corresponding cyclized product 3g.

The oxidative addition of pure (R(P))-menthyl phenylphosphinate 1 to a platinum (0) complex proceeds readily with retention of configuration at the chiral phosphorus center which was unambiguously confirmed by an X-ray analysis. In the presence of a catalytic amount of palladium, the hydrophosphinylation of a variety of alkynes with 1 also takes place stereospecifically, with retention of configuration, affording high yields of the corresponding vinylphosphinates bearing a single chirality at phosphorus.

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