Anft -Markovnikov

On combination with alkene hydroboration, the resulting two-step process is a very important, widely-used transformation which may be regarded as anft-Markovnikov hydration of the alkene (Equation B2.6). 

Addition to atkenes. Although this reagent has been studied mainly for electrophilic fluorination,1 it does add to alkenes to give cis-selective vic-fluoro alkyl sulfates with some preference for anft -Markovnikov addition. The adducts can be converted into fluoro ethoxysulfates by reaction with (C2H5)jO+BF4 .2... 

Subsequent studies have demonstrated that the relatively robust and readily accessible rare-earth trisamide La N(SiMe3)2 3 can also be successfully employed to catalyze anft -Markovnikov hydroboration of alkenes (28) [82], The 1,2-addition product in the hydroboration of vinyl arenes constitutes the opposite 2,1-addition products commonly favored in vinyl arene hydrosilylations (Sect. 3.1), although both reactions are believed to proceed via analogous mechanisms. This fact may also be interpreted in terms of uncatalyzed addition of the borane to the alkene being competitive with the catalyzed process in some cases [82,83],... 

Trivinyl benzene may be utilized in a hydroamination/carbocyclization process that is initiated by an intramolecular anft -Markovnikov addition of n-propylamine followed by an intramolecular hydroamination and a highly diastereoselective car-bocyclization step (44) [100]. 

Keywords S-vinyl compound, methanethiol, anft-Markovnikov addition, gas-sol-id reaction, thermal, photochemical... 

DFT calculation revealed the origin of the (Z)-selectivity of the anft -Markovnikov hydroalkoxylation of terminal alkynes (122), catalysed by the rhodium(I) 8-quinolinolato carbonyl chelate (123). The reaction is likely to commence by the formation of the // -complex PhC=CH[Rh], which tautomerizes via a 1,2-hydrogen shift to generate the Rh(I) vinylidene complex PhCH=C=[Rh]. Methanol, as an oxygen nucleophile, then attacks the Ca, and via the transition state (124), which is 1.2kcalmol lower in energy than its stereoisomer, thus giving the (Z)-vinyl ether (125). An improvement in the (Z)-selectivity in the related Rh(I)-catalysed 0... 

Scheme 17 Selected examples of mthcmium catalysts giving preferential anft -Markovnikov addition...

Cationic gold complexes are useful catalysts for anft -Markovnikov-t5q)e hydrothiolation with excellent regio- and stereoselectivities (Scheme 19) [56]. 

Reagent 30 reacts with alkenes 31 to give the corresponding products of p-azido-iodination (32) (Scheme 5.18). These reactions predominantly afford products of anft -addition with Markovnikov regiose-... 

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