Dienes steroid

The addition of (TMS)3SiH in the 3-oxo-l,4-diene steroid-type derivative promoted C(9)—C(10) bond cleavage (Reaction 7.68) [79]. The removal of the silyl group was achieved by treating with dilute aqueous hydrochloric acid at room temperature and the final product was obtained in an 85 % yield. 

R. Rona, L. Tokes, J. Tremble, and P. Crabbe, Synthesis of olefins and dienes Steroids, Chem. Commun. p. 43 (1969). 

Photochemical cycloadditions of homodienes are extremely rare. An unusual photocycloaddition of the 3-OXO-4,6-diene steroid 28 to 2,3-dimethylbutadiene has been reported.The reaction has been described as a [(27H- 27t) -t- (2n + 2a)] cycloaddition, but can also be explained as a sequence of two independent processes, a [(2n + 2n) + (2n + 2a)] and a [27c- -27t] addition (both photochemically allowed). 

Ether cleavage. Silica gel on which oxalic acid is deposited hydrolyzes enol ethers. This reagent is useful for converting 3-methoxy-2,5(10)-diene steroids (Birch reduction products of A-aromatic steroids) into the corresponding 5(10)-en-3-ones. For the cleavage of other ethers in methanol, the silica-alumina gel (prepared by the sol-gel method) is very valuable. The ease of deprotection follows the order TMS > 1 -methyl-1 -methoxyethyl 1 -ethoxyethyl > THP methoxymethyl. 

The silane is superior to the tin reagent in the radical rearrangement of glycosyl halides to 2-deoxy sugars (eq 14). Aromati-zation of the A-ring of 9,10-secosteroids can be achieved by a mild, radical-induced fragmentation reaction of 3-oxo-1,4-diene steroids (eq 15). ... 

Keto-l,4-Diene, 3-Keto-4,6-Diene, and 3-Keto-4,9(ll)-Diene Steroids... 

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