3-Methyl-3-buten-l-yne

The complex OsHCl(CO)(P Pr3)2 reacts with 2-methyl-l-buten-3-yne to give the dienyl derivative Os ( )-CH=CHC(Me)=CH2 Cl(CO)(P,Pr3)235 in 86%, which is a result of the selective addition of the Os—H bond of the starting complex to the carbon-carbon triple bond of the enyne (Eq. 4). 

The elongated dihydrogen complex OsCh -fFXCOXP1 Pr3)2 also reacts with 2-methyl-l-buten-3-yne. In toluene at room temperature, the reaction affords the alkenylcarbene derivative OsCl2 CHCH=CMe2 (CO)(P,Pr3)2 in 50% yield, after 1 h (Eq. 7). 

Preparation. The reagent (1) is prepared by the addition of methanol to 2-methyl-l-buten-3-yne using a catalyst prepared from red mercuric oxide, trichloroacetic acid, boron trifluoride ethcratc, and methanol. 

A similar example is seen in the [Pd2(dba)3]-catalyzed hydroboration of 2-methyl-l-buten-3-ynes [274]. While PPhj and PPh2(CgF5) favor the 1,4-addition product allenylborane 100 all diphosphines yield the 1,2-addition product ( )-dienylborane 102 exclusively (Table 1-13). This remarkable difference in selectivity is explained based on an 1,3-enyne monophosphine complex 103 and an alkynyl diphosphine complex 104 as intermediates. Dppf exhibits the best product yield among the phosphines tested. Similar observation was noted in the asymmetric hydroboration (Scheme 1-44) [275]. The action of catecholborane on 1-phenyl-1,3-butadiene also proceeds regioselectively to give, after oxidation, anti-l-phenyl-l,3-butanediol... 

Methyl- l-butene-3-yne Methylbutyl ether Methylbutyl sulfide... 

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