Benzyl Isopropenyl Ether

A soln. of benzyl isopropenyl ether in dry acetone added dropwise at room temp, under Ng during 2 hrs. to a stirred mixture of dry acetone and BFg-etherate, the product isolated after 16-18 hrs. 4-benzyloxy-4-methyl-2-oxopentane. Y 52%. F.e. s. J.Albaiges et al., Synthesis 1972, 378. 

Related Reagents. Benzyl Isopropenyl Ether 3,4-Dihydro-2i/-pyran 2,2-Dimethoxypropane Ethyl Vinyl Ether. 

With a secure route to pentacyclic amine 2, the completion of the total synthesis of 1 requires only a few functional group manipulations. When a solution of 2 in ethanol is exposed to Pd-C in an atmosphere of hydrogen, the isopropenyl double bond is saturated. When a small quantity of HCI is added to this mixture, the hydro-genolysis of the benzyl ether is accelerated dramatically, giving alcohol 15 in a yield of 96%. Oxidation of the primary alcohol in 15 with an excess of Jones reagent, followed by Fischer esterification, gives ( )-methyl homosecodaphniphyllate [( )-1] in an overall yield of 85 % from 2. 

C-Glycosyl derivatives may be prepared by utilizing glycosyl fluorides. Ishido and coworkers reported that the reaction of 2,3,5-tri-O-benzyl-a-(36a) or - -D-ribofuranosyl fluoride (36fi) with isopropenyl trimethylsilyl ether under BF3 catalysis (0.1 -0.05 mol. equiv. for the fluoride, in ether or acetonitrile) gave a mixture of 4,7-anhydro-5,6,8-tri-C)-benzyl-l,3-dideoxy-D-altro- (139, major) and -D-a//o-2-octulose (140) 139 was stated to isomerized to 140 (should be vice versa) under Lewis acid catalysis. Similar... 

Isocyanate, chlorosulfonyl-, 56, 41 Isocyanate, 2-propyl-, 56, 96 Isocyanide, benzyl-, 55, 98 Isocyanide, butyl-, 55, 98 ISOCYANIDE, tert-bulyl-, 55, 96 Isocyanide, cyclohexyl, 55, 98 Isocyanide, dodecanyl-, 55, 98 Isocyanide, ethyl-, 55, 98 Isocyanide, methyl-, 55, 98 Isocyanide, phenyl-, 55, 98 Isophorone, 57, 113 Isopropenyl acetate, 57, 113 Isopropyl alcohol, 58, 78,157 Isopropyl ether, 58, 45, 52 Isopropyl fluoride,58,78 Isopropylurea-polystyrene, 56, 96 Isoquinohne, 56, 20... 

More recently, van der Donk and coworkers reported radical cyclizations catalyzed by vitamin B12 using titanium(III) citrate as a stoichiometric reducing agent (Fig. 69, entry 17) [330]. Here /V-allylic 2-(isopropenyl) pyrroles 290 or allyl 2-phenylallyl ethers serve as the starting material in tandem hydrocobaltation/ radical 5-exo cyclization sequences giving dihydropyrrolizine derivatives 291 or 292. The mechanistic course is not completely clear. However, it is assumed that the reactions start with an initial hydrocobaltation of the isopropenyl unit in the presence of the allylic alkene (see Sect. 5.7). The benzylic cobalt intermediate is subject to homolysis of the very weak cobalt-carbon bond and initiates the radical 5-exo cyclization. Interestingly, the fate of the cyclized radical is dependent on the... 

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