Solvolytic rearrangement

Scheme 3.4 Proposed reaction mechanism for the deprotection and solvolytic rearrangement reactions of pHP caged phosphates like HPDP consistent with the TR, fs-TA and fs-KTRF experiments described here and in references 49 and 134.

In the synthesis in Scheme 13.46, a stereoselective aldol addition was used to establish the configuration at C(2) and C(3) in Step A. The furan ring was then subjected to an electrophilic addition and solvolytic rearrangement in Step B. 

Unusual cationic species, e.g. nonclassical bicyclobutonium ions, are discernible in the solvolytic rearrangements, depending on the structure of the substrate.3,4 Computational studies using ab initio at the STO 4-31G level of theory indicate that the molecular symmetry of the unsubstituted parent cation C4H, is a bisected form of the cyclopropylmethyl system.5... 

Solvolytic rearrangement of formic acid gave quantitatively the most stable product of the homoallyl rearrangement, e.vu-bicyclo[3.2.1]oct-2-en-7-yl formate (10). In 70% aqueous dioxane buffered with triethyl-amine at 80°C, the same tricyclic dinitrobenzoate 9 furnished a mixture of 78% tricy-clo[3.2.1.02 7]octan-3-ol (11) and 22% c.w-bicyclo[3.2.1]oct-2-en-7-ol (12).21... 

Another important study is that of the participation of heterocyclic moieties in the solvolytic rearrangement of /3-arylethyl tosylates,246 in-... 

An efficient route to 7-oxocamphene involved as its key step the solvolytic rearrangement of 3,3-ethylenedioxyisobomyl tosylate (derived from camphor-quinone).621 Brief (3 min 0 °C) treatment (PCl5-CaC03) of borneol gave excellent yields of camphene hydrochloride longer reaction times gave bornyl chlorides.522... 

Transformation of santonin (1) into guaianolides has been carried out by two different methods, namely photochemical rearrangement of the dienone system present in the A ring of santonin, and solvolytic rearrangement of a proper 1-sulfonate derivative. 

A methodology based on a solvolytic rearrangement of 1-sulfonate eudesmanolides has been extensively used by Ando [38]. Although this methodology has been shown to have wide applicability, the long step sequence required for the functionalization of C(l) constitutes a serious drawback. 

The overall yield of this synthesis was poor and so the same authors devised a new sequence starting from compound 206, obtained from santonin in 10 steps in 23% overall yield (Scheme 27). Solvolysis of 206 gave, in 75% yield, a 2 1 3 mixture of guaianolides 207, 208 and 209, which possess tetra-, tri-, and di-substituted double bonds, respectively. It is likely that the solvolytic rearrangement of206 proceeded via 210, since... 

Worthy of note are some generalizations as to the migration ability of different migrants made by British investigators in studying the solvolytic rearrangements of secondary alkyl tosylates ... 

Photochemical addition of allene to the enal (228) results in formation of a product (229 R = CHO), whose stereochemistry was established by conversion into the mesylate (229 R = CHjOMs) and solvolytic rearrangement ofthe latter to (230 R = Hand Ms). Thus, the stereochemistry of addition of allene is in accord with the theory of Wisner, i.e. the ground state of the allene adds to the more stable configuration (228a) of the excited state of the enal. ... 

The proposed intermediate (308) in the solvolytic rearrangement of homopropargyl derivatives (307) to cyclopropyl ketones and cyclobu tan ones has now been trapped. Thus, the cyclobutene (309) has been isolated from treatment of (307 R = Me, Y = OTf) with trifluoroethanol and sodium carbonate. ... 

Transannular sulfur participation occurs in certain solvolytic rearrangement reactions. Hence under pinacol rearrangement conditions either glycol (53) or (54) is converted to the bicyclic derivative (55). A possible mechanism for the formation of (55) from (53) is shown in Scheme 1. There appears to be no simple pathway to (55) from (54). Three possible pathways leading to the necessary ring expansion are shown in Scheme 1. 

No less ingenious is the synthesis of hirsutene by Tatsuta etal. in which the key step is the solvolytic rearrangement of (96) to (97), a process which probably provides a general entry to other members of this class of compound, since (96) is readily accessible by photocycloaddition. 

Tatsuta and his co-workers use a very different approach in their superb synthesis of coriolin. The key step is the solvolytic rearrangement of (97) to (98). Compounds such as (97) are easily prepared by [2 + 2]photocycloaddition, which makes this apporach a very efficient one for the synthesis of this type of compound. 

For solvolytic rearrangements the substrates 362a and 362b were prepared from cyclohexanone 4 [115]. The two stereogenic centers were introduced in both relative configurations by a proper choice of the conditions. Thus, diastereomer 365... 

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