Borates alkynyl

This process was first illustrated by Binger and Roster in 1974 (Scheme 17).35 Taking advantage of the readily available alkynyl-borates 21 (obtained by addition of alkynyl lithium or sodium compounds to triorganylboranes),36 the PBs 22a-d were prepared in good to excellent yields. During their investigation of the stereoselectivity of this... 

The reaction of -butyl tellurium bromide with alkynyl borates 112 is used to prepare (A )-vinvlic tellurides 113 as shown in Scheme 67.1... 

The other methods which involve organoboranes for the synthesis of trisubstituted alkenes employ either trialkyl(l-alkynyl)borates or trialkyl(l-alkenyl) bora-... 

Boron reagents add to conjugated carbonyl compounds. Alkynyl borate esters (p. 815) give conjugate addition in the presence of boron trifluoride ethe-... 

Alkynylboranes as useful synthetic intermediates are stronger Lewis acids and are easily hydrolyzed compared with alkylboranes. The Pd-catalyzed reaction of stable methoxy(alkynyl)borate complexes 71 derived from alkynyllithium gives arylacetylenes and stereodefined enynes 72 efficiently [Eq. (27)] [40]. 

Benzodithiolium perchlorate (218 R = H, X = CIO4) is highly explosive. Its 2-methylthio-derivative (218 R = MeS) condenses with 1-ethylaminonaphthalene to give the stable quinone-methide imine (219). Lithium trialkyl(alkynyl)borates Li R 3BC=CR (R R = n-CsHn or n-C6Hi3) react stereoselectively with the salt (218 R = H, X = Bp4) to produce vinylboranes (220) in high cis itrans ratios, which on hydrolysis and... 

Heterocycles. Alkenyl and aryl boronates deliver their organic residues to the opposition of the nitrogen atom of cyclic carbinolamines to replace the hydroxyl group. Synthesis of 2,3,5-trisubstituted furans, from a catalyzed reaction of alkynyl borates and enones, is achieved in one step. 

Scheme 5.2-117 The Mannich reaction with alkynyl borates in [BMIM][BF4] [262].

A few studies have been carried out on coupling of alkynyl borones. The stable methoxy(alkynyl)borate complex 158 was prepared in situ by the treatment of B-methoxy-9-borabicyclo[3.3.1]nonane (157) with alkynyllithiums or potassium reagents, and used directly for the coupling with halides to afford a variety of the disubstituted alkynes sueh as 159 [72,73]. 

A section on alcohol-forming reactions is included in a recent review of organo-bocates (such as cyano-, alkenyl-, and alkynyl-borates) in organic synthesis. 

An intriguing methodology for the organocatalytic asymmetric Michael addition of alkynyl borates to enones was reported by Chong in 2005 [99]. In this methodology BINOL derivatives are used as a catalyst and constitutes an example of a... 

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