Polyene cascade cyclizations mediated by BF3·CH3NO2. an unusually efficient method for the direct, stereospecific synthesis of polycyclic intermediates via cationic initiation at non-functionalized 3° alkenes. An application to the total synthesis of (±)-taxodione.

Biomimetic Cyclizations of Functionalized Isoprenoid Polyenes: A Cornucopia of Synthetic Opportunities

“…As expected, the reaction proceeded with no racemization at C-6 and produced an almost equimolecular mixture of cis-and trans-67. (4) Livinghouse studied the polyene cascade polycyclizations of different isoprenoid substrates containing an allylic or benzylic cyano function, demonstrating the preparative advantages of BF 3 (gas) in MeNO 2 over Hg(OTf) 2 -N,Ndimethylaniline complex or Brönsted and Lewis acids as reaction promoters [51]. (4)), were accessible from the 1,6-diene 63, resulting in a deterioration of the cyclization diastereoselectivity.…”

The boron trifluoride nitromethane adduct

“…It was first described as a superior catalyst for cyclization reactions [16][17][18][19]. From 1992 to 1994 its use in preparing annulations [20][21][22] of trienoate and of (7)-taxodione was published based on Harring's 1992 Ph.D. dissertation from the University of Minnesota [16]. It has also been shown to be a remarkably efficient catalyst in the creation of stereospecifically pure enantiomers [23][24][25] and opening ring structures allowing substitutions or creating linear compounds [26][27][28][29][30][31][32][33].…”

Facile Access to Optically Active Ring C Aromatic Diterpenes from (+)-manool. Synthesis of (+)-13-Hydroxypodocarpa-8,11,13-Triene, (+)-7-Deoxynimbidiol and (+)-Nimbidiol

“…10 To date, a number of synthetic investigations of these biologically active podocarpane diterpenes have been reported by * Correspondent: E-mail: jvillami@ivic.gob.ve employing podocarpic acid, labdane diterpenes or via polyene cyclisation. [11][12][13][14][15][16][17] However, they generally require long reactions sequences, and furthermore, almost all of them produce the racemic form of the natural substance.…”