143836-99-1Relevant articles and documents
Diastereoselective osmylation and hydroboration of β,γ-unsaturated n,n-diisopropylamides and acid-catalyzed conversion to δ-lactones
Vedejs,Kruger
, p. 4790 - 4797 (1999)
The title reactions of β,γ-unsaturated N,N-diisopropylamides occur with useful diastereofacial selectivity. The major diol isomer from osmylation of alkenes 1, 10, 11, and 12 in the presence of TMEDA at -78 °C corresponds to the facial preference shown in transition state model 41 (R(z) = H), while the opposite preference for 42 is observed with the Z-alkene 13. (Table 1). Hydroboration with 9-BBN does not show this inversion of diastereofacial selectivity for the Z-alkene. All of the results in Table 2 correspond to the usual preference for a transition state such as 45. Acid- catalyzed lactonization of the alcohols obtained in Tables 1 and 2 can be carried out with overall retention of configuration to afford δ-lactones. Butenolide 5 was prepared with 90% ee from alcohol 2a via osmylation followed by acid-catalyzed lactonization to 3 and elimination using SOCl2/pyridine.
An Efficient Entry Into Butenolides: Synthesis Of (+/-) Mintlactone
Chavan, Subhash P.,Zubaidha, P. K.,Ayyangar, Nagaraj R.
, p. 4605 - 4608 (2007/10/02)
Osmylation of β,γ-unsaturated esters and acid catalysed cyclisation of the resultant diols generate butenolides in high yields.
