Bicyclo mesylate

However, Adcock, Shiner and coworkers found increased rates of solvolysis for 4-metalloidal-substituted bicyclo[2.2.2]-oct-l-yl p-nitrobenzenesulphonates and methanesulphonates, in the order tin>germanium>silicon73, as also observed for the fi-effect. The relative rate of solvolysis of the 4-trimethylsilyl mesylate 63 compared to the non-substituted parent compound was 49 1. 

This mechanism also accounts for the very large 5-deuterium isotope effect observed for the solvolysis of (4-D)bicyclo[2.2.2]oct-l-yl mesylate. This mechanism is also supported by theoretical calculations of 4-substituted bicyclo[2.2.2]oct-l-yl cations74. 

Adcock, Shiner and coworkers found a significant 48.6-fold rate enhancement for the 4-trimethylsilyl bicyclo[2.2.2]octyl mesylate 265 compared with the silicon-free analogue 266102. The effects of trimethylgermyl and trimethyltin groups in the 4-position (in 267... 

The solvolytic behaviour of C(3)-substituted 2a,5-epoxy- and 2a,5-epithio-5a-cholestanes has been compared with that of the simple bicyclo[2,2,0]heptane derivatives, and their 7-oxa- and 7-thia-analogues. The 3a-(cxo)mesylates solvolysed at unexceptional rates, with migration of the anti-periplanar C(l)-C(2) bond resulting in ring contraction to give A-nor products (see p. 298). The... 

Transannulation of the mesylate (33), derived from 4,8-dimethylcycloocta-4-en-l-ol, using sodium carbonate in aqueous dioxane has provided the bicyclo[3.3.0]octanol (34), a central precursor to the monoterpene iridomyrmecin (35 equation 13). In studies of the biomimetic synthesis of the natural tri-quinanes capnellene (37 equation 14) and pentalenene (40 equation IS) Pattenden et al. have shown that both molecules can be produced from appropriate cycloocta-l,S-diene precursors, i.e. (36) and (39) [or indeed their corresponding positional isomers (38) and (41), respectively] by treatment with boron trifluoride. Mehta et al. have described an alternative transannulation approach to the triquinane unit found in pentalenene, i.e. (42) - (43 equation 16), and also to the ring system (44 equation 17) found... 

Mesylation of annulated bicyclo[2.2.2]octenol 29 in the usual way initiates a spontaneous cationic cyclization to trachylobanate alcohol 30 in 40% yield. Mesylation followed by addition... 

X = Cl, Br) were treated with potassium tert-butoxide in tetrahydrofuran to give 80% and 40% yield, respectively, of 7,7-dichloro- and 7,7-dibromo-2,3-bis(methylene)bicyclo-[4.1.0]heptane (19, X = Cl, Br). Elimination of the corresponding bis(mesylates) (see Section 5.2.2.3.) gave only low yields of bis(methylene) products. 

A double mesylate elimination using potassium /ert-butoxide in tetrahydrofuran was attempted as a means of preparing 7,7-dichloro-2,3-bis(methylene)bicyclo[4.1.0]heptane (14, X = Cl) and its 7,7-dibromo analog from the corresponding diols. However, only low yields of the dienes... 

Solavetivone (661) has also been a synthetic objective with two new syntheses having been completed. The first of these (Scheme 63) achieved syntheses of both solavetivone (661) and the hydroxy derivative (675), whose glucoside has been identified in tobacco.302 The second synthesis (Scheme 64) relied upon a Diels-Alder reaction to construct a bicyclo[2,2,2]octyl framework which was then cleaved by acid to release a prenyl-mesylate (679) for further acid-promoted... 

Synthesis from xylose The xylose derivative 47, obtained from 5,5-bis-benzyloxy-7-oxa-bicyclo[2.2.1]hept-2-ene (45), has been used in the synthesis of (-P)-castanospermine (1) (Scheme 6). Bromination of 45 occurred exclusively on the less hindered convex face of 45, followed by stereoselective migration of the endo OBn group of the acetal to give 46, which subsequently converted to 47. Mesylation of 47 followed by cyclization with ammoifia gave 48, whose protection, hydrolysis, acetylation and cyclization by an intramolecular Wittig-Homer condensation gave 49. Conversion of 49 into epoxide 50... 

Methanesulfonyl chloride added at 0° to l-methyl-l-(2-hydroxyethyl)-1,2-di-hydronaphthalene and dry pyridine, stirred 18 hrs. at room temp., the soln. of the resulting crude mesylate in wet benzene-petroleum ether chromatographed over basic alumina, and eluted with ether exo-l-methyl-2,3-benzo-bicyclo [3.2.1]-4-octanol. Y 54%.—This is a remarkably facile ring closure through double bond participation. W. Herz and G. Gaple, Am. Soc. 84, 3517 (1962). 

Bravetti et al. have devised a very simple regio- and stereo-specific synthesis of the noraphidicolane (64) and norstemadone (65) ring systems from the common bicyclo[2.2.2]octane intermediate (59) (Scheme 5). The intermediate (59) was prepared by the Wiesner two-carbon annulation sequence involving (i) photocycloaddition of allene to the cyclohexenone (57), (ii) conversion of this into the masked aldol (58), and (iii) retro-aldolization. After conversion into the mesylates (60) and (62), acetolysis gave the respective bicyclo[3.2.1]octane derivatives (61) and (63), which were elaborated to (64) and (65) respectively. 

One-bond disconnection via Path C generates bicyclo[3.3.1]nonane intermediates. Keto-mesylate 7 is a l,5-difimctional intermediate one might convert to twistane via yet a third intramolecular alkylation. This is the pathway pursued by Hamon and Young. ... 

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