Homopropargylic amines, addition

The Pd-catalysed addition of boronic acids to homopropargylic amines (93), carried out in the presence of formaldehyde, is believed to proceed via the Pd-coordinated formaldiminium ions (94), affording )V-alkyl-3-alkylidenepyrrolidines (95) as a result of the overall iyn-addition across the C=C bond. " ... 

The additional a-substitution in allenylborane reagents such as 25,28, and 30 compared to 17 enhances the enantioselectivity for the propargylation of aldehydes. However, this effect is particularly apparent in their additions to /V-H aldimines, which produce homopropargylic amines in good yields (91%), but disappointing ee (from PhHC=NH, 73% ee). With 32 (325 935677-62-6 32/ 929082-37-1), the homopropargylic amine 33 is produced as essentially a single isomer (51-85%, >99 syn, 92-99% ee) (eq 13). ... 

Enantioselective synthesis of homopropargyl amines can be effected through copper-catalysed reaction of an allenyl boron reagent with aldimines. The first nucleophilic allylation of r-electrophiles by allylboron reagents has been achieved enantioselectively using a chiral rhodium catalyst (Scheme an allylrhodium intermediate has been implicated. Similar additions of R CH=CR BF3K have also been reported. ... 

In a subsequent study, Miginiac and coworkers examined additions of allenylzinc reagents to an ZV-TMS imine derived from the mono diethyl acetal of acetylene dicarboxaldehyde10. These additions afforded the homopropargylic adducts as the free primary amines (equation 13). 

As a general rule, allylic organozinc reagents do not react with unactivated a, ji-disubstituted alkynes. A few exceptions to this trend have been observed in the case of substrates bearing an appropriately located heteroatom such as the homopropargylic tertiary amine 147. The latter reacted regioselectively with allylzinc bromide but led to a 67/33 mixture of two geometric isomers, apparently derived from syn and anti additions (equation 71)82,105. 

Intramolecular additions of alcohols or amines to olefins are recognized as useful methods to provide heterocyclic compounds. Kozmin and Zhang have achieved a gold-catalyzed synthesis of heterobicyclic alkenes by double cyclization of alcohols or sulfonamides which have a 1,5-enyne moiety [175]. As a typical example, unsaturated alcohol (95) is smoothly converted to 6-oxabicyclo[3.2.1]octane (96) in 90% yield using a 5 mol% of AuCls catalyst (Scheme 18.34). Cyclic ethers are also available from homopropargylic ethers with pendant alcohols through gold-catalyzed... 

---