Phenyl tetrazolyl ethers

A case in point is hydrogenolysis of the 1-phenyl tetrazolyl ether of tyrosine, to phenylalanine 107). 

Metalation of phenyl tetrazolyl ethers 377 (Scheme 124), either direct or by bromine-metal exchange, triggered the heterocycle migration from oxygen to carbon [158]. Products were obtained in excellent yields for all examined derivatives (84-93%). Again, a spirocyclic four-membered ring intermediate was involved. Similarly, naphthyl derivative 380 smoothly rearranged to 381. 

Conventionally phenyl tetrazolyl ethers have been employed for the removal of an OH group. Addition of a mixture of an ethereal solution of phenyl 5-(1-tetrazolyl)ether and a catalytic amount of dichloro[1,3-bis(diphenyl-phosphino)-propane]nickel(ll) introduced dropwise into refluxing sec-butyl-magnesium chloride under nitrogen followed by reaction for 10 minutes afforded upon work-up,sec-butylbenzene in 77% yield (ref. 101). 

An improved method for the removal of methylenedioxy-groups in alkaloids of the benzylisoquinoline and tetrahydroberberine series has been derived. Alkaloids such as remneine (26) can be converted into the dihydroxy-bases (27) by treatment with boron trifluoride followed by 5-chloro-5-phenyl-l//-tetrazole and subsequent hydrogenolysis of the resulting bis-tetrazolyl ethers. The yields in the process are good.39... 

Hydrastine has been prepared by the hydrogenolysis of the 1-phenyl-l/f-5-tetrazolyl ether of (—)-a-narcotoline,154 and in the racemic form by the reductive cyclization of the quaternary salt of the keto-acid (53) that is obtained from oxidoberberine (51) as described above.133 The lactone (80), prepared by the dye-sensitized photo-oxidation of oxidonorcoralyne followed by reduction with sodium borohydride and from 6 -acetylpapaveraldine by oxidation with hypo-bromite followed by reduction, has been TV-methylated and reduced with sodium borohydride to an isomer of cordrastine.133 Cordrastine itself has been synthesized by the electrolytic reduction of a mixture of the iminium salt (81) and bromomeconine (82), a process that has been shown to be of general applicability to the synthesis of alkaloids of this group.155... 

Recently, a new and efficient synthesis of cyprodime from naltrexone (2) has been reported [73], Firstly, the tetrazolyl ether (27) was formed by reaction of naltrexone with 5-chloro-l-phenyl-1 Ff-tetrazole [74], Catalytic hydrogenation afforded 3-deoxynaltrexone (28) which was methylated with dimethyl sulphate to give the enol ether (29). Acid hydrolysis gave the known morphinanone (30) [75] which was treated with activated zinc and ammonium chloride to yield the phenol (31). 4-O-Methylation with phenyltri-methylammonium chloride afforded cyprodime (23, Scheme 3.4) [75],... 

A transfer hydrogenation modification has been described of a known dehydroxylation procedure (ref.52) in which the phenyl ether with 1-chloro-2-phenyltetrazole is used. The tetrazolyl ether stirred in benzene/ethanol/water (7 3 2) with 10% Pd-C was treated dropwise with 64% aqueous hydrazine, with TLC monitoring for completion of reaction, to give naphthalene in 82% yield (ref.53). 

A. Preparation of the Phenolic Ether p-(l-Phenyl-5-tetrazolyl-oxy)biphenyl. In a 1-1. round-bottomed flask fitted with an efficient condenser is placed a magnetic bar for stirring. Seventeen grams (0.1 mole) of p-phenylphenol, 18.1 g. (0.1 mole) of... 

Unsubstituted tetrazolyl derivative 458 was also prepared according to the following procedure (91MIP2). A solution of 5-phenyl-2-trityltetrazole in tetrahydrofuran was first treated with 1.7 M ferf-butyllithium in pentane at -25°C, in two parts. After about 30 minutes, an organolithium salt precipitated. Then a 1 M ethereal solution of zinc chloride was added to the mixture, which was then warmed to room temperature. Bis(triphenyl-phosphine)palladium(Il) chloride and 4//-pyrido[l,2-a]pyrimidin-4-one 457 were added to the reaction mixture, and after boiling for 4 hours, the 2-trityl derivative of 458 was obtained in 56% yield. Finally, detritylation with a mixture of methanol and concentrated hydrochloric acid yielded tetrazole derivative 458. 

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