Alane cleavage

Sulfur analogs, 2-tetrahydrofuranyl and 2-tetrahydropyranyl thioethers, were reduced by alone to alkyl 4- or alkyl 5-hydroxyalkyl thioethers resulting from the preferential reductive cleavage of the carbon-oxygen (rather than the carbon-sulfur) bond. Thus refluxing for 2 hours with alane in ether converted 2-alkylthiotetrahydrofurans to alkyl 4-hydroxybutyl thioethers in 63-72% yields, and 2-alkylthiotetrahydropyrans to alkyl 5-hydroxypentyl thioethers in 58-82% yields [794]. 

Two quite different methods have been developed for sequencing DNA. One method, developed by Walter Gilbert and Alan Maxam and involving cleavage of preexisting DNA, uses a chemical approach. A second method, involving premature termination of newly synthesized DNA, uses an enzymatic approach that was developed by Fred Sanger. 

The late Alan Ritzer of GE wrote of the opportunities that environmental regulations present to silicone manufactures118. A major strategy of GE Silicones continues to be avoidance of landfilling and incineration and returning key materials back into commerce. Said Ritzer, Additional opportunities remain as overall silicon utilization still can be further improved . Residue cleavage represents one method to create more Di and Tri. Mono and Tri redistribution (equation 8) represents yet another method to improve Di yield. 

Apart from alanes [108-110], and monochloroalanes ([111] for use of mono-chloroalanes in the reduction of 2-azetidinones to azetidines, see [112]), boranes have also been employed for the (3-lactams N -C2 bond cleavage. Baldwin had reported the sodium borohydride promoted ring opening of A-Cbz (3-lactams... 

The disilyl derivative of all-cix-1,2-epoxycyclopentane-3,5-diol 5 7 was treated with diethyloctynylalane to afford after cleavage of the silylether function the triol 58. This triol was convered via the acetonide to the benzyl ether 59. Hydrolysis with aqueous trifluoroacetic acid yielded the diol benzylether 60 which could be prepared by an alternative route as well. This route proceeds via the monotrityl epoxide 61 and benzylation to the trityl benzylether 62 and then reaction with diethyl octynyl alane to the diolbenzylether 60 and the isomeric 1,3-diol. 

Table 6 Cleavage of Tetrahydrofuranyl Benzyl Ether with Alanes in Ether at Room. Temperature (2 h) ...

Another sequencing technique is the Maxam-Gilbert method (developed by Alan Maxam and Walter Gilbert). In this method, a single DNA strand is labeled at the 5 end with radioactive phosphorus (P ). The radioactive DNA is divided into four portions and each one is exposed to different chemical reactions. Each reaction causes a 5 cleavage adjacent to either... 

At elevated temperatures the reaction may be applied to alkali tetra-ethylalanate and the alkali trialkylalkynyl alanate is formed with cleavage of alkane (30) ... 

For alkynes with terminal acetylenic bonds, hydrogen cleavage is a competing reaction, dependent on the acidity of the C—H group, and this leads to alkynyl alanes (68, 209, 235) ... 

Reaction between 1-alkynes and trialkyl alanes goes uniquely in the sense of alkane cleavage if trialkylaminetrialkyl alanes are used. At 100°-120°C, trialkylaminedialkylalkynyl alanes are obtained in practically quantitative yield (31) ... 

Hydroaluminadon. A stereoselective approach to cycloheptenols is based on the cleavage of 8-oxabicyclo[3.2.1]oct-6-enes. The lack of generality for the fragmentation protocol plagued the method. Now a useful procedure consists of Nilcodl -catalyzed hydroalumination and treatment of the alane with i-BUjAlCl. This method is also appropriate for the asymmetric synthesis of cyclohexenols. 

N-Aziridinylphosphorus compounds. A soln. of methyl 3- m-[bis-(l-aziridinyl)-phosphinylamino]phenyl)-N-phthaloyl-DL-alanate and 1 mole of hydrazine hydrate in methanol stirred 4 days at room temp. crude methyl 3-(m-[bis-(l-aziridinyl)phosphinylamino]phenyl)-DL-alanate (Y 89%) dissolved in methanol, treated with 1 mole of methanolic ANa-methoxide and some water, allowed to stand 20 hrs. at room temp. -> Na-3-(m-[bis-(l-aziridinyl)phosphinylamino]-phenyl)-DL-alanate (Y 83%).—Aziridine derivatives such as the above ones are quite sensitive to ring cleavage by acids. F. e. s. A. P. Martinez, W. W. Lee, and L. Goodman, J. Med. Ghem. 7, 224 (1964) selective removal of the phthalyl group in dimethylformamide, peptides, s. M. Bodanszky et al.. Am. Soc. 86, 4452 (1964) in isopropanol s. A. F. Rosenthal and M. Pousada, R. 84, 833 (1965). 

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