Abstract:A one-pot procedure for the efficient hydroazidation of alkenes involving hydroboration with catecholborane followed by reaction with benzenesulfonyl azide in the presence of a radical initiator is described. The regioselectivity is controlled by the hydroboration step and corresponds in most cases to an anti-Markovnikov regioselectivity. This procedure is applicable to a wide range of alkenes and gives excellent results with 1,2-disubstituted and trisubstituted alkenes.
“…On the basis of the Li precedent, we propose that Ag III -mediated oxidation of the alkyl(Bpin) species 2 generates the homobenzylic radical 24, [12] which undergoes cyclization onto the nitrile to afford the nitrogen-centered radical 25 (Scheme 2). [15] Thea dvances described here,i nvolving the cyclization of alkylBPin derivatives with nitriles,thus provide an important complement to previously developed radical cyclization processes involving alkylborane precursors. [15] Thea dvances described here,i nvolving the cyclization of alkylBPin derivatives with nitriles,thus provide an important complement to previously developed radical cyclization processes involving alkylborane precursors.…”
Section: Wanxiang Zhao and John Montgomery*mentioning
An efficient two-step method for the assembly of indanone derivatives starting from as imple vinyl arene has been developed. The sequence first involves addition of bis(pinacolato)diboron (B 2 pin 2 )a nd N-cyano-N-phenyl-pmethylbenzenesulfonamide (NCTS) to ab road range of styrenes by utilizing IMesCuCl as catalyst. This step simultaneously accomplishes hydroboration of the alkene and ortho cyanation of the benzeneunit. The products thus obtained are further functionalized by aA gNO 3 /Selectfluor-mediated coupling of the BPin and cyano functionalities to annulate anew five-membered ring. This combined two-step sequence provides av ersatile method for the site-selective derivatization of abroad range of vinyl arene substrates.
“…On the basis of the Li precedent, we propose that Ag III -mediated oxidation of the alkyl(Bpin) species 2 generates the homobenzylic radical 24, [12] which undergoes cyclization onto the nitrile to afford the nitrogen-centered radical 25 (Scheme 2). [15] Thea dvances described here,i nvolving the cyclization of alkylBPin derivatives with nitriles,thus provide an important complement to previously developed radical cyclization processes involving alkylborane precursors. [15] Thea dvances described here,i nvolving the cyclization of alkylBPin derivatives with nitriles,thus provide an important complement to previously developed radical cyclization processes involving alkylborane precursors.…”
Section: Wanxiang Zhao and John Montgomery*mentioning
An efficient two-step method for the assembly of indanone derivatives starting from as imple vinyl arene has been developed. The sequence first involves addition of bis(pinacolato)diboron (B 2 pin 2 )a nd N-cyano-N-phenyl-pmethylbenzenesulfonamide (NCTS) to ab road range of styrenes by utilizing IMesCuCl as catalyst. This step simultaneously accomplishes hydroboration of the alkene and ortho cyanation of the benzeneunit. The products thus obtained are further functionalized by aA gNO 3 /Selectfluor-mediated coupling of the BPin and cyano functionalities to annulate anew five-membered ring. This combined two-step sequence provides av ersatile method for the site-selective derivatization of abroad range of vinyl arene substrates.
“…[2] Owing to the rich chemistry of organic azides, [3] the hydroazidation reaction represents ap articularly attractive process.T he addition of hydrazoic acid and its derivatives (TMSN 3 and NaN 3 )t on on-activated olefins is difficult and limited to substrates forming stable tertiary and benzylic carbocations. [6] This reaction provided the corresponding products with excellent anti-Markovnikov regioselectivity (Scheme 1). [5] Recently,w ed escribed ar adical procedure for the hydroazidation of alkenes using catecholborane as the hydroboration agent followed by reaction with benzenesulfonyl azide as ar adical trap.…”
A one-pot procedure for the enantioselective hydroazidation of non-activated trisubstituted alkenes is described. Hydroboration with monoisopinocampheylborane (IpcBH ) provides dialkylboranes that are in situ selectively converted into monoalkyl-substituted catecholboranes; these undergo radical azidation upon treatment with benzenesulfonyl azide and a radical initiator. Enantiomerically enriched azides were thus obtained in yields of 59-81 % and enantioselectivities of up to 94:6 e.r. (98:2 e.r. if the intermediate dialkylborane is purified by crystallization). A rapid access to enantiomerically pure (+)-rodocaine is also described. The use of other arenesulfonyl radical traps enables enantioselective hydroallylation, hydrosulfanylation, and hydrobromination reactions with yields of 71-86 %.
“…93 This procedure is applicable to a wide range of alkenes and gives excellent results with mono-, di-, and trisubstituted alkenes (equation 130). β-Citronellene underwent 6-exo-trig cyclization to afford the corresponding organic azide at a high concentration of benzenesulfonyl azide (equation 131).…”
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